If Stu Hamm and Tony Levin are together, I would bet money that the show would kick some serious ass, regardless of who the other is. As for you second question, staying in "the pocket" is pretty much another way of saying "keep it simple". Just keeping a fairly simple groove going is staying in the pocket (I'm 90% sure of that, I might be off). And chops: I've heard different explanations, all I can tell you is that to have chops is a good thing.
Edit--I just noticed the question mark after Tony Levin in your first post. Don't know who he is? Check out his site:
www.tonylevin.com. He's extremely talented and played with damn-near everybody, from Peter Frampton to King Crimson to 3 members of Dream Theater working a side project called Liquid Tension Experiment.. (plus I love the sound of the Stick).