B is hit or miss for me. When it's nice, it's really nice. When it's crowded and overwhelmed it's really crowded and overwhelmed. No real in between IME.
As for the best club in ATL, I'm torn between E and the ramp level D club (i.e. NOT the old UA Club turned SC). E has the best food generally. All the offerings of the other clubs plus it always has the Sky Bowls station for afternoons and evenings. TATL bank in mid afternoon/early evening is too crowded for me usually, especially the bar. Otherwise it's generally great.
The ramp level D club is almost never crowded, has ample, comfortable furniture, cool views out the top windows, decent food and bar, and the best restrooms of all the ATL clubs. All single person, individual rooms, and IME, never a line.
The only thing I like about F is the quiet room no one seems to be aware of and is usually empty even at peak times.