It appears that Las Vegas and Charlotte are the only airports with a current or announced Centurion lounge but no Skyclub. At airports with both, I expect that the Skyclub is typically more convenient for Delta flyers. No doubt there will be in initial novelty attraction, but in the long run I anticipate it will be minimal - and Delta may have insisted on reciprocal access to continue to admit Platinum and Centurion cardholders to Skyclubs.
Honestly at SEA, the Skyclub is nicer anyway except for the alcohol selection, but the fact is that even where there is overlap, there will be additional strain on Centurion.
I'm glad you did the research on where there wasn't an overlap b/c when I first saw the announcement I was curious.
Per-visit access to Sky Clubs increases to $39
Any guesses as to how long before that applies to vanilla Amex Platinums?