I'm going with the Bionic when it's released...while it may have a pretty screen, the US GS2 is just a bunch of speculation at the moment...my reasons...
1. Bionic has 4G (my area is supposed to be getting 4G within the next 60 days) and I want that speed!
2. I don't really care about rooting...I rooted my first OG Droid back in the day, but I found myself not doing anything with it that I couldn't do when it was unrooted. And as with all DIY projects, when something is wrong you have to service it yourself...and frankly, I'm lazy and don't want to fiddle with it constantly. It's not for me. I'd only justify rooting if Moto Blur annoyed the crap out of me...but I've played with it some on my mom's Atrix and it doesn't seem too bad.
3. I don't have detailed enough vision to really see that much of a difference between the Pentile and Super AMOLED or whatever it's called. The Bionic's screen looks awesome from the pictures I've seen, so I'm satisfied.
I'll pass on the GS2...the Bionic has everything I want.