This idea that a 1060 will 'comfortably' max out games at 1080p is quite misguided. It's basically a gtx980 in Pascal form. I have a 1070 and while I max out FC4 for instance there are plenty of frame dips; same with ROTTR, and Deus Ex:MD I haven't tried but I'm pretty sure it will flatten my GPU. You want to get the best card you can get.
As for 1070 vs 980ti, I had both and I really can't tell a difference. They're essentially the same card, give or take. If the ti is cheaper, like say R6-6500, get it. Otherwise the TDP difference and heat management makes the 1070 a better bet. My 980ti Lightning had 3 power pins versus 1 in the 1070.