Both titles have a lot of heart and have given me quite a few laughs. I have to go with Ultimate Spider-man because it's such a good character piece for both Peter and Miles. You see real development in both characters. I do love Bendis's earlier work on New Avengers though. It was a fun book with a lot of cool superhero ideas--like what he did with the prison break out and Secret War and all that. The initial team had a great mix of personalities.
It's just cool that so much of Bendis's work is being mined for live action stuff. It's not hard to see why.