1070 TI over 1080 Definitely, As all of Nvidia x80 series cards have always lead to be the one of the worst choices for gamers due to the fact that You get very similar performance for a cheaper price in the 1070 TI, and if you want performance better than a 1080, you just go for a 1080 TI.
It was same situation in the 900 series where a majority of the people bought a GTX 970 or a GTX 980 TI, leaving those that purchased a GTX 980 feeling quite hosed off and also feeling like their money was poured down the sewage drains.
1070 TI over 1080 to prevent any emotional antsy feelings from occurring.