In terms of efficiency, that is hashrate per kilowatt-hour, which GPU is the best?
I assume you're asking this question because you have expensive power?
Looks like most people like the 1080 Ti, and it is a strong hasher, but it depends.... on:
1. What algorithm are you going to mine? I only mine equihash, so that's all I can comment on right now. If you want to mine cryptonight etc, then disregard
On Equihash, a 1080 Ti can get 700-800 Sol/s, with the most efficient settings getting around 725 sol/s and using 250 watts.
A 1070 Ti can get 525-650 Sol/s, with the most efficient settings getting around 570 sol/s using 170 watts.
None of that is even CLOSE to the most efficient settings for those cards on equihash.
1080 ti running at 150 watts will pull 620 sols, for about 4.1 sols/watt vs YOUR less than 3.0 figure.
1070 ti running at 106 watts will pull around 460 sol/s for over 4.4 sols/watt.
*SOME* but not all 1080 models can match that 1070 ti efficiency, but they usually want a little more power to run efficiently and end up at slightly lower efficiency as a result - but STILL well over 4.0 sol/watt at their most efficient.
Those are both using EWBF and are long-term averages, NOT cherry-picked "one reading" peak numbers.
I'd have to SEE 650 sol/s out of ANY 1070 ti to believe it (one time peak readings do NOT count), even if you're running DTSM or Bminer vs my normal use of EWBF (both of those seem to offer a LITTLE more hashrate at high power settings, same to a hair less at efficient settings).
The 1080 ti is a "higher density" card than the 1070 ti, but it's a little LESS efficient (even after factoring in "system power draw per card" for both).
It's pretty close either way though when figuring on a per-rig basis.