For cold hardy my experience has been that Musa sikkimensis Daj Giant has been the fastest, followed by Musa cheesmanii(but I did save my fastest M.cheesmanii seedling out of about 60 seedlings).
Overall I would definatly say Ensete ventricosum is the fastest when given room.
Here's an Ensete ventricosum grown from seed in zone 9 on the cool CA coast which rarely gets up to 80F(mostly in the high 60's in summer), but also only freezes a few times in the winter.
It's around 2.5 years old, grown in dune sand with lawn clippings, and not watered hardly enough.
