the 7D offers far better AF performance than the 5D2, and would be my pick in that comparison, especially if you're only going to have one camera. i own a 5D and love it - it's superb for landscape work - but the 7D is a better choice for all-around photography.
the 5D Mk II has more resolution than the 7D, and though the AF and frame rate aren't as good, it's probably a better choice for general and landscape photography due to its superior resolution (21Mp) and high ISO performance. unfortunately, it also costs about $1000 more than the 7D.
basically, if you're planning on a lot of landscape or portrait work, go for the 5D. if you plan to shoot mostly general photography, sports, or wildlife, the 7D is the choice hands down. for what it's worth, as soon as i can afford it, i plan to buy a 7D as a replacement for my 40D for wildlife work.
Last edited by squirl033; Apr 30, 2010 at 8:57 PM.