I was trying to think of things that a exo-planet has that would affect vegetation-ability that we would be able to know about.
I.E. size of planet(maybe), and distance from the sun.
Though I don't know if we're too close to the sun, thereby heating up the equator and giving us deserts, or too far from the sun, thereby freezing water and locking it up to prevent in-land regions from getting to it.
I'm thinking it's the latter, based solely on the fact that in this context, we have no real way of knowing how much water is on those other planets. At best, we can tell how much water is in the atmosphere, and I think that's only a recent thing we can do. So without knowing how much water is in it's hydrosphere, the "higher vegetability" would be a planet that has no chance of having frozen water.
Is my thinking, at least~
*Note: Since we don't know the land-areas and water-content of most of these planets, it's totally possible for a planet to have a thin film of water on a barely-bumpy planet, or have a pangaea-like continent. One would make it so EVERY place on that planet is within a few hundred miles of water, so very few deserts, and the other would almost certainly create a massive in-land desert. These two scenarios would skew a planet that would otherwise be poor/rich in vegetation to the opposite end, simply because of geography that we can't actually see from earth.