Either one will suffice for me, just looking more into cost efficient, also something that will last hopefully 3 years or so.
I am stuck in a pickle here, because any of the cards will be more than enough for what I use it for, Mostly league, and a couple side games.
When I built my current computer, I put a 560ti in it (500 series were current at the time). It lasted until about a year ago, when I replaced it with a 970. In all reality, though, if that 560ti were still alive, I'd still be running it (it could run League fine at a steady 60fps). The 960, especially with the 4gb of memory, should be more than enough and still last quite a while, even if you do start playing something a little more graphically taxing than League.
One side comment regarding my 970: Because I have the 970, I decided to get a 144hz monitor. The 970 seems to be able to pull a steady 140-144 fps for me in League. My 560ti would not have been capable of that. The 960 would come much closer, of course, but I would expect it to be a tad weaker than the 970 (that should be obvious). So if you're wanting to run a 144hz setup, that would probably be the only reason I'd opt for the 970 over the 960.
Go with a motherboard that supports crossfire/sli and get a gtx 960 for now. Make sure it has two hdmi ports on it to support both monitors, and if you decide you are going to play higher end graphic games than you can get a second card later.
