This one is easy, I will chose Batista in a landslide. Its not that hard, when is the last time Khali put on a good match, how about never. Khali is too big to wrestle and the idea of him wrestling is pointless because he would pretty much kill anybody he faces. When Khali wrestles you get one of two things, he wins in 10 seconds or he loses a horrible match, thats about it.
Batista on the otherhand is one of the top stars in the business and receives too much criticism. Batista put on what I would consider the best match against Undertaker at Wrestlemania 23, something that Khali could never do. Anybody who can steal the show at any Mania' should be considered one of the top current stars int he business, Khali on the other hand put on a stinker at Mania' 23 in a match vs. Kane. Batista is far and about better than Khali and there really is no argument the other way except for saying that the fact that Khali is so huge, but he isn't dominant enough to be considered a monster anymore, any big match he is in he loses.
Based on all of that, it is obvious that Batista is way better, at least he has the potential to put on a great match and actually wins from time to time.