I would say I would want to go to the Washington Redskins, on these grounds:
+they have a defense that was good last year and projects to be better this year with their young pass rushers and lineman, they might even be ready to "win now" on the defensive side of the ball
+Washington has a lot of cap room and the capacity to bring in Peyton Manning with a high salary, as well as Reggie Wayne and Jeff Saturday to help keep him comfortable, given him a good target, and secure the offensive line
+their coach did well with John Elway at the sunset of his career, and won two Super Bowls with him, so I do not see a reason he could not do the same with Manning in the next couple of years
+Santana Moss, Roy Helu, etc. so the Redskins at least have some weapons for Peyton to work with, and certainly no worse than the stuff he left behind in Indianapolis (besides Harrison and Wayne)
+the NFC East is actually something of an empty shell right now... the Eagles were overrated and #7 is on his way out, the Giants are really streaky, and the Cowboys are teetering between getting old and starting to rebuild again
+they have a high draft pick that could turn into an offensive lineman or a new receiver for Manning to rely on for the next couple of years
Of course, Washington would have a lot of downsides, too...
-the NFC is (overall) stronger than the AFC at current
-he would have to pay Eli twice a year for that circus
-Washington has a habit of signing big name free agents that flop
-I don't know how well Manning would get along with Dan Snyder
-it is a big market in a big market division, and I think Manning might want to stay in a place where the national media under-reports you in flyover country
I just think the team itself and the cap space gives them the most to work with Manning and in bringing around his supporting cast. I don't know if it will actually happen, but I figure the offer of, "a good, young, gelling defense, a top-10 pick of an offensive player of your choice, and as much of your support cast from the Colts that you are wanting, in a division with no obvious roadblocks." Washington had abysmal quarterback play last year, and Manning might be their ticket to turning that around finally. Of course, same could be true of a few other contenders, like Kansas City and Arizona, too.