I am 80% determined to get a 1070.
1080 has a bit more performance but I don't like the price tag.
The performance / value factor is clearly in favour of 1070. I keep an eye on performance tests and I see the 1070 being over 980Ti, that's good enough for me. I still use a 970 so the difference will be noticeable.
Pricing will make a big difference for me - if I can get a OC model 1070 at something not too silly I'll probably grab one as a stopgap until the bigger cards that said still having a hard time justifying replacing my 780 - most of what I'm playing at the moment runs fine at 2560x with it and a G-Sync monitor the only thing that struggles is Doom (which still runs fine at 1920x1080) but that is partly due to some performance bug or something - takes 3x the performance hit going from 1080p to 1440p compared to the delta in any other game going between those resolutions.