So the 7770 will still be better even though it only has 1GB of VRAM.
EDIT: Sorry ilumunus, I really don't mean to come across as just wanting to smash everything you say or something, I just want the OP to be informed as good as possible and not to make a wrong decision.
Assuming it surfaces at the $150 target Nvidia tells us to expect, the GeForce GTX 650 Ti offers the best performance at its price point, with average frame rates that outclass the Radeon HD 6850. The Radeon HD 7770 is beaten even more soundly. Conservative power, heat, and noise measurements make the card easy to live with and build an entry-level gaming system around, too
Between those 3: 550-Ti, 650 and 7770. The Radeon 7770 wins.
It's true that for a little more money the 650-Ti will perform a bit better so it's also a very good choice. If you can stretch even more money and really want to see a huge bump in performance the next logical step would be the 7850:
Go with the 550-ti, I had so many problems with AMD in the past (driver and hardware issues)
Nvidia also had their share of problems with their hardware or drivers (Remember the Vista drivers fiasco which almost took them a year to fix, or all those 8600-GTS dying, the list could go on). I'm not a fanboy, right now I'm running a GeForce but I would have no problem switching to a Radeon. I had both ATI and nvidia products in my life and never ran into any problems with both. Drivers issues with AMD are greatly exaggerated, they might have run into some minor issues some years ago, but it's all been solved for a long time now the new drivers are very stable. It's funny how some people still refer to that today as something to consider... You would have to prove that new AMD drivers don't work well on new products like the 7770. The problem you encountered in the past are probably linked to an older generation of hardware coupled to an older generation of drivers so your argument doesn't apply today.