Version: 0.34.11
Mods: Lazy Newb Pack.
Modified creature_standard.txt to avoid different sizes for dwarves.
[PHYS_ATT_RANGE:STRENGTH:1250:1250:1250:1250:1250:1250:1250] +
[PHYS_ATT_RANGE:AGILITY:1250:1250:1250:1250:1250:1250:1250] -
[PHYS_ATT_RANGE:TOUGHNESS:1250:1250:1250:1250:1250:1250:1250] +
[MENT_ATT_RANGE:ANALYTICAL_ABILITY:1250:1250:1250:1250:1250:1250:1250] +
[MENT_ATT_RANGE:FOCUS:1250:1250:1250:1250:1250:1250:1250] ++
[MENT_ATT_RANGE:CREATIVITY:1250:1250:1250:1250:1250:1250:1250] +
[MENT_ATT_RANGE:PATIENCE:1250:1250:1250:1250:1250:1250:1250] +
[MENT_ATT_RANGE:MEMORY:1250:1250:1250:1250:1250:1250:1250] +
[MENT_ATT_RANGE:SPATIAL_SENSE:1250:1250:1250:1250:1250:1250:1250] ++
[BODY_APPEARANCE_MODIFIER:HEIGHT:100:100:100:100:100:100:100]
[APP_MOD_IMPORTANCE:500]
[BODY_APPEARANCE_MODIFIER:BROADNESS:100:100:100:100:100:100:100]
[APP_MOD_IMPORTANCE:500]
full leather armor

full metal armor

New LNP Nov 16, 2013 (dwarffortress with Urist Da Vinci's Patch)
Arena results (500 rounds - 1 dwarf vs 1 dwarf):
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 259 |
| Dwarf | Gold War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 241 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 247 |
| Dwarf | Gold War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 253 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 257 |
| Dwarf | Gold War Hammer | full leather | Grandmaster hammerdwarf/armor user | 243 |
Platinum total wins 763
Gold total wins: 737
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 262 |
| Dwarf | Copper War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 238 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 259 |
| Dwarf | Copper War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 241 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 251 |
| Dwarf | Copper War Hammer | full leather | Grandmaster hammerdwarf/armor user | 249 |
Platinum total wins 772
Copper total wins: 728
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 270 |
| Dwarf | Silver War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 230 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 262 |
| Dwarf | Silver War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 238 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 251 |
| Dwarf | Silver War Hammer | full leather | Grandmaster hammerdwarf/armor user | 249 |
Platinum total wins 783
Silver total wins: 717
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 279 |
| Dwarf | Steel War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 221 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 252 |
| Dwarf | Steel War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 248 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 262 |
| Dwarf | Steel War Hammer | full leather | Grandmaster hammerdwarf/armor user | 238 |
Platinum total wins 793
Steel total wins: 707
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 274 |
| Dwarf | Iron War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 226 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 261 |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 239 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 256 |
| Dwarf | Iron War Hammer | full leather | Grandmaster hammerdwarf/armor user | 244 |
Platinum total wins 791
Iron total wins: 709
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 500 |
| Dwarf | Adamantine War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 0 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 500 |
| Dwarf | Adamantine War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 0 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster hammerdwarf/armor user | 488 |
| Dwarf | Adamantine War Hammer | full leather | Grandmaster hammerdwarf/armor user | 12 |
Platinum total wins 763
Adamantine total wins: 737
Conclusion: All metal materials tested (except adamantine) seem to be doing the same for war hammers against leather armor, almost the same against iron armor (highest is 11% difference between gold and silver) and there is a small diference when hitting adamantine armor (highest is 21% difference between platinum and steel).
The results are:
Platinum>=Gold>Copper>Silver=Steel=Iron
Old LNP (dwarffortress without Urist Da Vinci's Patch)
Arena results (100 rounds - 1 dwarf vs 1 dwarf):
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 59 |
| Dwarf | Gold War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 41 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 35 |
| Dwarf | Gold War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 65 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster armor user | 45 |
| Dwarf | Gold War Hammer | full leather+iron | Grandmaster armor user | 55 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster armor user | 50 |
| Dwarf | Gold War Hammer | full leather | Grandmaster armor user | 50 |
Platinum total wins 189
Gold total wins: 211
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 53 |
| Dwarf | Steel War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 47 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 53 |
| Dwarf | Steel War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 47 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster armor user | 51 |
| Dwarf | Steel War Hammer | full leather+iron | Grandmaster armor user | 49 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster armor user | 41 |
| Dwarf | Steel War Hammer | full leather | Grandmaster armor user | 59 |
Platinum total wins: 198
Steel total wins: 202
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 54 |
| Dwarf | Iron War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 46 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 51 |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 49 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster armor user | 54 |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster armor user | 46 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster armor user | 53 |
| Dwarf | Iron War Hammer | full leather | Grandmaster armor user | 47 |
Platinum total wins 212
Iron total wins: 188
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 100 |
| Dwarf | Adamantine War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 0 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 100 |
| Dwarf | Adamantine War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 0 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather+iron | Grandmaster armor user | 85 |
| Dwarf | Adamantine War Hammer | full leather+iron | Grandmaster armor user | 15 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Platinum War Hammer | full leather | Grandmaster armor user | 95 |
| Dwarf | Adamantine War Hammer | full leather | Grandmaster armor user | 5 |
Platinum total wins 380
Adamantine total wins: 20
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Silver War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 55 |
| Dwarf | Iron War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 45 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Silver War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 56 |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 44 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Silver War Hammer | full leather+iron | Grandmaster armor user | 38 |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster armor user | 62 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Silver War Hammer | full leather | Grandmaster hammerdwarf/armor user | 109 |
| Dwarf | Iron War Hammer | full leather | Grandmaster hammerdwarf/armor user | 91 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Silver War Hammer | full leather | Grandmaster armor user | 56 |
| Dwarf | Iron War Hammer | full leather | Grandmaster armor user | 44 |
Silver total wins 314
Iron total wins: 286
Ironx10 is the same than iron but with 78500 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 57 |
| Dwarf | Ironx10 density War Hammer | full leather+adamantine | Grandmaster hammerdwarf/armor user | 43 |
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster armor user | 55 |
| Dwarf | Ironx10 density War Hammer | full leather+iron | Grandmaster armor user | 45 |
Iron25 is the same than iron but with 25000 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 40 |
| Dwarf | Iron25 density War Hammer | full leather+iron | Grandmaster hammerdwarf/armor user | 60 |
Iron20 is the same than iron but with 20000 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 51 |
| Dwarf | Iron20 War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 49 |
Iron15 is the same than iron but with 15000 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 44 |
| Dwarf | Iron15 War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 56 |
Iron5 is the same than iron but with 5000 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 61 |
| Dwarf | Iron5 War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 39 |
Iron4 is the same than iron but with 4000 solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 51 |
| Dwarf | Iron4 War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 49 |
Iron0.2 is the same than iron but with 200 (as adamantine) solid_density instead of 7850.
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 100 |
| Dwarf | Iron0.2 War Hammer | full leather+Adamantine | Grandmaster hammerdwarf/armor user | 0 |
Iron low impact is the same than iron but has
[IMPACT_YIELD:50000]
[IMPACT_FRACTURE:50000]
Iron high impact is the same than iron but has
[IMPACT_YIELD:5000000]
[IMPACT_FRACTURE:5000000]
| Creature | Weapon | Armor | Skills | Rounds won |
| Dwarf | Iron low impact War Hammer | full leather+iron | Proficient hammerdwarf/Grandmaster armor user | 56 |
| Dwarf | Iron high impact War Hammer | full leather+iron | Proficient hammerdwarf/Grandmaster armor user | 44 |
Conclusion: All metal materials tested (except adamantine) seem to be doing the same for war hammers with no noticeable difference (at least against armored enemies).
Less density might give advantage over high densities due to the bug reported by Urist Da Vinci (weights with a large decimal values are more important than densities)
Very high impact yield and very high impact fracture gave no advantage against very low impact values.