Back to the original post: don't know about Southwest but I just flew ATL-PHX in 737 and compared to 767 that used to fly on this route it wasn't the best experience even with upgrade. Same goes for ATL-DFW: they used to have 767's and 757's, now it is mostly 737 and some of them are with one class configuration.
I've recently had a chance to experience AA FC on ATL-DFW and was very impressed: it is like in the good old days on Delta even if their flight attendants somewhat less enthusiastic - choice of meals, drinks in real glasses, no paper placemats etc. Compared to that, Delta has certainly moved toward Southwest standards...