The Titans had Nicks and Britt rated nearly identical. Neither would have been reaches at #30. I like both WR's a lot.
Britt had the 3rd longest arms among the WR's at the combine. The knocks about his catching/drops is because he tends to catch the ball with his body. His strength, physicality, and long arms make him the best blocking WR in the draft, at least out of the top guys. Better leaper than Nicks, and is faster and taller. A good route runner coming out too, and can get through jams.
Nicks had the 2nd biggest hands. Has questionable work ethic/discipline after gaining nearly 20 lbs. due to not being able to work out because of an injury. He has an inconsistent motor, and he's just an average blocker. Better body control than Britt, and uses his hands to catch the ball away from his body. Isn't as fast as Britt, but is better after the catch with his good balance. Good route runner too, but it will still be hard for him to get separation consistently.
Britt is an all-around WR, and Nicks is a possession guy. As I said, I like both a lot, but with Britt being a better down-field threat and better blocker, he fits Dinger's scheme better.
Also, to clarify a few misconceptions:
I don't know who said Britt was strictly a possession guy, but that's wrong.
I think 40-times for offensive skill positions are vastly over-valued. Running good routes cause more separation than pure speed. But, Britt's 40-time of 4.47 is just fine. Maclin ran a 4.46 40, and Britt has 20 lbs. on him.
Rey Maualuga is best when he moving straight ahead. He would struggle in the Titans Cover 2. He'd have to be taken out on 3rd Down, and could be a liability with his aggressiveness. Would the Titans change their philosophy on drafting the MIKE position early if a can't miss prospect is available? Yes, but that prospect is not Maualuga.