A longer frame makes it easier to do most things, like front tap, etc, and I found that switching to a longer bike helped my bunnyhops. Depends how and what you ride, but on the whole longer bikes are better. I wouldn't go as long as say 1100 as I think I'd find it harder to ride... 1055 suits me fine.
Lower bikes are a lot better as you get more clearance. If you look at the recent Bristol pictures thread, see how when people sidehop super high they crouch right over the side of the bike. Also, smaller frames tend to be lighter and stiffer.