I'm going through the same Azazl but my 980's are the EVGA SC reference cards, so moving to a 1080 (can't decide between EVGA FTW or MSI Gaming X) will move me away from SLI and offer a quieter PC, more VRAM for the 1440p screen and a smoother experience.
I remember moving from GTX680's to a 780Ti and although it was similar performance, as would be the case here, I noticed a massive difference in smoothness. BF4 around the time played much better on the single card.
My past experiences with SLI have never been good i use a lot of race sims so do really notice if the frames are not smooth SLI was a nightmare for small glitches, micro stutter ect
Single card is all ways for me much smoother
There is this ....one of the old technique's used many years ago and still used for DAW (digital audio workstations) running on multi core cpu systems. Its not a wonder boost for fps but what this does is may get rid of them nasty little glitches you may get...can also help with getting rid of all types of micro stutter...
http://www.coderbag.com/programming-c/disable-cpu-core-parking-utility