In most titles the 6700k will outperform the R7. Consider the 6700K a slightly ( 200Mhz ) slower 7700K. The chips perform identically at the same clock speeds.
https://www.gamersnexus.net/guides/3009-amd-r7-1700-vs-i7-7700k-144hz-gaming
Only the Intel 8600K and 8700K beat the 7700K ( which is a tiny bit faster than a 6700K ) for pure gaming purposes.
Edit: I should add Intel chips are seeing a performance hit with this Spectre/Meltdown malware to the point they have stopped updates. So who knows where they will end up when all's said and done. The AMD chips are relatively unaffected compared to Intel so it might be a safer choice to go with AMD.