The showers at A are the BEST in AA's system, hands down (at least IMHO)--the "personal car wash" as I call them. The mini-gym is right next to them. The old Flagship Lounge/Arrivals lounge area is a in-airport oasis of undistrubed quiet.
The "atmosphere" at D is the brightest, and the D concourse has the best restaurant offerings, if that's important.
I'd say go grab a run on the treadmill & a shower at A, & linger at will there at will, then skylink over to D for a meal & post-meal relaxing at the club there.
I'm pretty convinced that the staff rotate from club to club.