The only redeeming quality of the 7700K is that Intel was able to raise the turbo freq to 4.5 GHz, while the 1700X only boosts to 3.8 GHz. So yeah single-threaded perf will be higher with Intel.
I should add that the above is the main reason the kaby lake release is so lackluster. There is very little reason to upgrade your desktop to a 7 series (laptops get power optimization and 4k playback support).
It's also the main reason why AMD might look appealing, lack of worthwile upgrade from Intel while AMD delivers twice the cores/threads for not a gread deal more then a 7600K.
You're talking about Skylake 6-series, the 6900K is Broadwell-E not Skylake despite being 6-branded.