More vram for the 7970? = Doesn't matter. You don't need it.
But it's true, you don't
need it. No game right now needs 3GB of VRAM, or even 2GB of VRAM. Games today are still designed to require about 1GB of VRAM for rendering purposes. Anything extra is used for preloading assets, or for higher levels of AA and resolution.
I managed to play Crysis 3, Bioshock Infinite, Far Cry 3, Metro Last Light etcetera all with 1.5GB of VRAM on my GTX 580 SLI at the highest visual fidelity (except AA of course) at 2560x1440 and have very playable frame rates.
Now having switched over to GTX 770 4GB SLI, minus the obvious increase in processing capability, I find that games load much faster now, and area transitions are much smoother due to the increase in VRAM. I can also ratchet up the AA a lot higher if I want to.
Faster overall compute performance? = Doesn't matter. It's nothing you will ever use and it's only used in games by AMD to make nVidia look bad. You don't need to worry about that.
This does matter, but it's not especially salient because very few games use that feature and NVidia aren't exactly weak in compute either.
AMD's better dev relations lately? = Don't pay any attention to that. They are just unfair cheating Bast****. Don't fall for their tricks. Besides, they don't support CUDA or PhysX.
How does AMD have better developer relations? While it's true that AMD have been very aggressive lately in adding titles to their GE program, NVidia haven't been sitting on their laurels. Assassin's Creed IV, Splinter Cell Black List, Watch Dogs, Batman Arkham Origins, Witcher 3 are all AAA titles and TWIMTBP games.
What matters is that it uses moar power and has been available for over a year now. Speaking of over a year now, remember when it was $550? What a ripoff AMD is, eh! What? Titan? You want the best it's going to cost you. You're only whining because you're poor and beneath those who can afford to own truly the best, cost be damned.
Well I can tell you one thing, until AMD fix their Crossfire, they aren't even an option for me.