Nope, 970 SLI.
Random graphs from an unknown source really aren't proof of anything. Though, even still, the only game that had a noticeably lower minimum framerate was SoM, and my guess is they are using the idiotic HD textures to try to choke all the cards except the 980Ti(since the minimum requirement for the HD textures is 6GB of VRAM, they also don't improve image quality during actual gameplay any).
The SLI setup has been perfectly smooth for me. There is no stuttering. I run a 120Hz panel and keep every game I play over at least 75FPS at all times. The old microstutter issue has all but been eliminated with modern dual-core SLI setups.
Here's the thing, I bought the 970s back in 2014. This was a good 5 months before Titan X was even released, and the 980Ti wasn't even a rumor yet. So I had better than Titan X and 980Ti performance 5-7 months before hand, and for less month too. And I've continued to enjoy that great performance. I also don't like tearing apart my main rig, it is what I used for pleasure, I play games on it, and I have very little time to do that. So the less downtime the better. I don't tend to upgrade the video cards in my main rig that often. Before the 970s I had 670s, I could have put my 780Ti in it, but why waste the time for a sidegrade? Before the 670s I had 470s. I'm not going to waste time for marginal upgrades, or sometimes even sidegrades. So it isn't that I prefer the 970s, that wasn't the point I was trying to make. The point is the difference is so marginal it isn't worth the effort to swap the cards out.