4 960s vs. 2 980s?

[hhill19]

I had a random thought pop into my head. How do 4 GTX 960s in SLI compare to 2 GTX 980s in SLI (with the same CPU obviously)? I'm still relatively new to PC building and I don't know how specs "stack" when installing multiple GPUs.
What I'm interested in is how they compare in 4k.

 

[j-lor]

2 980s would be better. Usually you get little performance improvement when you go past 2 way sli.

 

[Mousemonkey]

And 960's are only 2 way SLi capable.