Look if you're getting the 980 then you need to invest in all round better build and for that reason the i5 is better , price/performance nowadays nothing beats the i5.
With that being said the i3 will do it for gaming as for now however if you can't afford an i5+980 then get the i5+970 , that will stand the test of time.
I5+970 OC will beat i3+980 at stock.