I would personally go for the 6600k and z170 combo as the processor is unlocked meaning you can overclock it at some point if you desire, combined with the feature set available on the z170 boards. As Trafalgar mentioned though you would get hyper-threading with the 6700 meaning for software that is able to utilise them then you would get a performance boost.
I use photoshop quite regularly and I think the 6600k would be more than sufficient with the 1070 as it can use the GFX to do some of the heavy lifting and that is a beast of a card.
Overall that is the best combination in my opinion.