It's hard to say but
for McCain, I think he should take serious consideration of Sarah Palin, Bobby Jindal, Charlie Crist or Mitt Romney. I think Rick Perry would be a good choice as well but he won't get picked since it would be too easy for the Dems to try to turn him into a "Bush III" since he was G.W.B's successor in Texas. Condoleeza Rice would do a good job but is too moderate socially to attract much of the conservative base that McCain needs. Besides, I think whoever McCain picks will likely be a governor.
Obama shouldn't pick Clinton. To do so would basically shoot himself in the foot. I am guessing he is probably looking at Bill Richardson, Tim Kaine,Phil Bredesen, Jennifer Granholm, Ed Rendell, Mike Easely, Kathleen Seibilus, or maybe even (although highly unlikely) Deval Patrick. Essentially, Obama will want to pick up either a woman or someone who is in charge of a large state or one that typically goes GOP. He, even more than McCain is likely to pick a governor to make it seem like at least someone in his administration has executive experience. The only reason I put Patrick on there is that the two are practically in bed together; writing eachother's speeches and such.
I have not given much thought to Obama's choice, but I agree with you on McCain. I hope he picks either Sarah Palin or Bobby Jindal. I don't like Romney very much, and I REALLY don't like Charlie Crist. I like Rick Perry, but I agree with your reasoning.
Right now I actually think Palin is a better choice than Jindal, although either would be fine.
(My first choice would have been Giuliani, but that is not an option that is being considered.)
My only real thoughts on Obama is that I agree with you that picking Hillary would be a mistake.