GTX 960 is cheap and better.It does play all games but GTA 5 is poorly optimized,so u may experience some stuttering with 960 due to 2GB vram (i faced same even though i get 60fps constant and with 2.6GB vram )but i also saw some ppl have stuttering even with GTX 970..So its not right to say its due to 2GB vram,just poorly optomized.
I played Shadow of mordor at ultra settings and texture at very high even though it says less vram avalable..I got 40-43 fps constant in map1 and 35-40fps in map2. Vram usage was ~3GB still i don't see any lag or stutter(2 times i see lag but no stutter).Very well optimized game. I pushed that far coz i wanted to experience the graphics of SOM.