Bynum hasn't done as much to impress me as Bargnani and Biedrins, but i can see flashes where i think he'll surely be a dominant centre in the league 5-7 years from now.
The reason i put Bargnani over Biedrins is simply because i'd rather have a 21/8 player instead of the Samuel Dalembert of the west. His whole career will be him putting up 15/16 one game and 6/5 in another. I just can't see him being consistent enough on offense to be great.
I won't say I feel Biedrins isn't tough mentally or phsically because I've haven't read anything like that, but Bargnani has the attitude where you don't think he'll be great, you know it.