I did ORD -MEM and then beyond several times recently on NW owing to involuntary reroutes by United because of late inbound to ORD. It is a really old DC-9 but the interior is pretty nice. I have also been on NW's ARJ's which have a small first class section and are much newer and have nicer interiors than the AWAC BAE146's which are older version of the same plane. The NW Memphis terminal is pretty nice and the gates that the NW regional carriers use are very nice and spacious.

At ORD NW uses some gates at the very end of the E concourse so its not too much nicer than the F gates but less chaotic because of fewer flights using the gates.