Depends of resolution are you usig and how you feel buying a ''old'' card like 980Ti.
for example, my case. i own a 1080p monitor, and i no see in the future upgrading it (mainly because in argentina we can't get 1440p monitors lol, and they're more expensive than a 4k monitor, unbelievable.) For me, both cards will perform amazing at my resolution for years i'm sure to say it, but they cost almost at the same price so, i would pick the 1070 without thinking it twice.