Delta Flight Museum - go see the 747
I spend as little possible time in Sky Clubs as possible please dont waste your time, but to answer your question about ATL ANY of them EXCEPT B and the one at D12
I am not sure why people like One Flew South at ATL so much especially when Atlanta has so many options for eating outside the airport. OFS is "ok" for an airport restaurant but "meh" if it was not at the airport.