If your employer will only reimburse an airline club membership Skyclub is the obvious choice for a Delta flyer.
Otherwise, American Express Platinum could be better because it includes Skyclub access when flying Delta and several other lounge networks as discussed here:
Centurion and Platinum airport lounge access: Airspace, Centurion, Delta, Escape
Amex Centurion and Platinum Priority Pass benefit
Note that you could try American Express Platinum free for one year, to see if the other lounges benefits are useful:
https://www.flyertalk.com/forum/amer...-one-year.html