The GTX960 is a Maxwell architecture that is more modern than the R9 cards.
They are more power efficient and some say better drivers.
From a performance point of view, any $200 card is going to perform about the same as any other.
Probably hard to tell without a synthetic benchmark.
Specs don't matter, the performance is what counts.
I suggest that a balanced gaming pc will budget 2x the cost of the cpu for the graphics card.
If you upgrade, make it a significant jump or you may be disappointed.
What is your current graphics card, cpu, and make/model of psu?