Both will OC to about the same limits.
So the question becomes which is more important... Graphics power or many threads.
Graphics power is most important in fast action shooters.
Multiplayer games tend to like many threads.
strategy games, sims, and MMO types tend to be single threaded and like faster single thread cpu performance.
If you can foresee a future upgrade to a GTX1080ti, then I would pick the i7-7700K.
I really like the 7600K, but for the $100 difference, the 7700K will be better in the long run.
The 7700K is a 91w processor.
It does not need exotic cooling even with a good overclock so long as your case has decent intake airflow.
Noctua NH-U14s or NH-D15s will do the job, here are the noctua tdp specs:
http://noctua.at/en/tdp-guide