I don't make a big deal about what kind of wood it is unless i'm buying it (which i don't). Pretty much any hard wood that is free works for me (soft woods (mostly pine) can cause creosote build-up in your smoke stack that can cause fires if you aren't careful). The problem comes that some woods burn to ash pretty quickly, leaving little substance for the coal bed. I learned this with my silver maple stash. Currently, I'm finding more wood for free than I can use, so I've been getting pickier and taking mostly locust, oak and ash. They seem to work well and are common in my area, though they can be quite a chore to split.
So you'll get heat out of all of em, but for buying wood already split, stick to the highest BTU wood available in your area.