Please tell me how that comment is productive to the debate? Seriously bro, we all know he spelled Belichick wrong, but there's no reason to just leave a comment that says just that. The OP brought up a real interesting debate, how bout you add something to the conversation rather than just make brash comments. You weren't funny.
Now, to the OP's question, I say Belichick. I really had to put a lot of thought into it. For one, you see a team like the Colts. It doesn't matter who the receivers or head coach are, Peyton will always keep that team in contention. I believe that Brady can do this as well, but not to the same extent (that's not to say I'd pick Manning for my team over Brady, I wouldn't).
Bill Belichick doesn't just shape players on the field, he is a talent evaluator. He has a system that works. Plus, in terms of longevity, Belichick would probably be around longer.
Just ask yourself this: If someone said, in 2011, that the Patriots would be losing Bill Belichick, what would you think? Would the Patriots be the same team? No, I feel like their identity would be completely changed.
But switch it around. Say Tom Brady wasn't there in 2011, would the Patriots be the same team? Of course not, it would suck. However, I still think they would have that PATRIOT IDENTITY, that would not exist without Bill Belichick.
It's a good thing this is just a hypothetical question though, eh?