As of now, there seem to be two favorites in contention for Manning's services. Denver is the current favorite, but Arizona is gaining ground and are optimistic about their chances.
Ultimately, Manning will choose Arizona.
The biggest reason has to be Larry Fitzgerald. Not only is he a terrific receiver, but the two of them have already met over dinner in Indy. Besides, who doesn't want to see what Fitzgerald can do when paired with one of the greatest quarterbacks of all time?
The Cardinals also have an ascending defense and a backfield that is loaded with potential. They have the cap room to bring in Dallas Clark and Reggie Wayne, which would make this offense just a decent offensive line away from being unstoppable.
But does Manning really need a great offensive line to be successful? After all, he almost won a Super Bowl in 2009 with one of the worst units in the league.
When you compare Denver's roster to that of the Cardinals, Arizona just has more elite talent.
Another huge advantage the Cardinals have over the Broncos is that they play indoors in a controlled environment. Why would a 35-year-old player with a bad neck want to deal with variable conditions when he does not have to?
Besides, the Cardinals know what it is like to bring in a veteran star at the twilight of his career and make it work.
To me, Denver is only the favorite because they were the first team to meet with Manning. But if you give the Cardinals some time, they make quite an impressive offer for the future Hall of Famer.