I had questions similar to OP's and recently had a good discussion with a couple of IRC regulars who know the internal guts of DF pretty well. Mostly just as stated in posts here.
Blunt: Silver, Copper
Edge: Adamantine, Steel, Iron, Bronze
Crossbows: usually Copper for bashing.
We also talked about bolts and shields.
Bolts: fairly even and lethal across the board as long as they are metal. They almost ignore any armour except chainmail shirts. They have an edge attack, which sometimes is directly converted to a blunt attack by armour, and a projectiles benefit from density. However, somehow all that has very little significance when it comes to actual testing, which I don't understand. Just avoid adamantine bolts (rare, useless vs adamantine armour), and save your wooden bolts for training and bone for hunting. If you have lots of spare silver, use it, otherwise use copper.
Shields: Any material offers essential and equal protection. But shields also bash, a blunt attack, so (Edit:
silver) copper is best for its density. Except for marksdwarves who are always well isolated behind fortifications. Use light wood (Edit: or leather) for shields for greater mobility with the same protection from elite archers.
We didn't talk about spears, which have both an edge and a blunt attack. Anyone chime in?
Crossbows: Since they're blunt in combat, Silver is a good choice for army marksdwarves.
Crossbows can't be forged from silver.
Crossbows: For fortress guard, the wiki suggests that bone, light wood, or candy will reduce beating severity, though there have been some disagreements on this of late.
I'm interested in reading this discussion if available. Link please.