Okay, I went and found the section(on page 29) where Sully discusses why he chose the flaps setting, for those who don't feel like checking out the entire interview. I assure you though, it's worth reading in its entirety.
Asked about the flap setting selected prior to landing, Captain Sullenberger said that he called for flaps 2 and believed that they achieved that because he saw FO Skiles move the flap handle, felt the flap extension begin and the aircraft made the movement and sound that the flap extension usually made, and he observed on his PFD on the speed tape that a lower speed was possible. Asked why he made the decision to continue the landing with Flaps 2, Captain Sullenberger stated that there were operational advantages to using Flaps 2 that became obvious to him. He knew that going to Flaps 3 would not give him much more of an advantage in terms of lowering the stall speed and drag would have increased. He said he was concerned about having enough energy remaining to successfully flare the airplane and reduce the rate of descent sufficiently for landing. From his experience, Flaps 2 would give him a slightly higher nose attitude when landing. He said he felt that in the accident situation, Flaps 2 was the optimum setting.