I think much depends on the aircraft you get (seatguru.com might be able to shed some light on that, if you know it). With NW, I'm not crazy about the DC-9s on the ATL-DTW run, but if you get 757s on longer hauls then the seats in those are OK.

NW definitely doesn't try to be tops when it comes to food. Seems like every meal they have was designed primarily to meet a cost ceiling. Would rate CO highest among DL/NW/CO on that, but you want to have the bird in the hand with CO, as I'd rate their coach on the same route the lowest.