Debatable indeed!
Personally, I see Helves and Humans as the top choices. Everyone always says "But WF can heal themselves! and +CON!!!!" But they forget that with a human sorc, even on a first life 32 point build, you can easily get UMD to a point where heal scrolls are at 90%+ for you. That's some real self-healing there! Helves are even better if you take the FvS Dilletante and spend some AP on it, because then you get all the divine scrolls/wands up to level 10 at 100% no matter what your UMD score is (though, really, what else are you gonna put skill points into? Balance?) And both of these choices offer no penalty to CON or CHA so you can max them both, even on a 32 point toon and start with 18's.
This leaves WF and Drow as second-rate choices for me. WF immunities don't matter much to me, but the fact that you can't wear robes does (which is most of the current caster armor, only a few good docents out there and most of them are VERY recent additions). The additional CON can be useful, but really it doen't give you THAT much more survivability than Human or Helf. Drow on the other hand take too much of an HP/CON hit, and with Savant Tier III abilities having their DC based on CON, this just spoils it for me. I know they're not super useful, but really it's nice for it to work when you do use it.
Horc is right out, though.