5770 512mb GDDR5 vs GT440 1GB GDDR5?

Which is better, the 5770 512mb GDDR5 or the GT440 1GB GDDR5? I've searched a lot of articles and reviews and the 5770 wins against the GT440. But those reviews were of the 1GB variant of the 5770, I don't know if it makes a difference. Is the 5770 512mb really THAT better than the GT440 1GB, or are they just almost the same. Plus nowadays in my country its a pain to search for a 5770, and a GT440 costs almost the same. Would I miss out on a lot and really regret buying a GT440 over a 5770 performance-wise? And these are pretty much the only cards that I can afford to buy. And on another note, what about the 6670?

I only game at a screen resolution of 1366x768, just want to play games at the highest possible settings with smooth frame rates (40fps+), AA maybe about 2x only since above that it's hard for me to even tell the difference. Would I be able to do that with either one of these cards with games like, Skyrim, DotA 2, Prototype 2, Starcraft 2, Diablo 3, etc.? Thanks.