Either way, this is a TWIMTBP game, and is optimized for NV cards. The graphics quality potential on the 770 is better than 3GB nin-NV cards
From what we are seeing a 770 2gb
can't enable ultra textures in Watch Dogs (or the new wolfenstein).
This breaks down more as 2gb vs 3gb+cards rather than nv vs amd. But the 3gb cards from AMD do have a nice bonus here vs the 2gb nvidia card, ie) 280x 3gb> 770/680 2gb in a case like Watch Dogs.
3gb cards can enable ultra textures. Provided cards with 3gb have enough performance to run Ultra the 3gb cards will be providing a better gameplay experience. If folks want blur filter of TXAA then that will benefit nVidia owners, i'm currently not aware of any other nVidia specific stuff besides TXAA in Watch Dogs.
But basically:
Ultra textures > High/Non Ultra Textures
Perhaps Ultra will be so minimally improving to gameplay that it won't matter, though we know it will be at least as good or better than high for gameplay experience.
Not sure what's unclear here unless 2gb cards can enable ultra textures and the reports saying they can't are wrong.
High should be fine, but Ultra is going to be better. It's a loss for 770/680 2gb owners, but this debate has been had on these boards many times, looks like the folks saying more VRAM is the best bet, ie) 280x > 770 2gb or if going 770/680 to get 4gb to be safe, were right. That's what these boards are suppose to achieve, little bit of banter (sometimes a lot) to get the right suggestion/result for other enthusiasts.
We also have confirmation that 2gb cards like the 770 are locked out of ultra textures in the new Wolfenstein and from [H] testing this doesn't appear to be an arbitrary lockout, 2gb's is not enough for ultra textures in wolfenstein.