One advantage to 7700k is that it can use Optane. Optane could be a product, like SSDs were, that become the norm. That's one advantage to 7700k. Another is, at stock the 7700k hits 4.5GHz whereas the 6700k only hits 4.2GHz. (but you can overclock it). If you really want to hit 5.0Ghz then 7700k is better.
@disinformatique. I will overclock the 7700k one day, but it isn't required for my needs now. 4.5GHz on single fan air cooler(quiet too) isn't bad. I'm also giving the delid some time to see if any changes occur or improvements to get a better baseline.