Welcome to FlyerTalk, 55Ford!

All I can say from experience about legroom is that I took a flight on NWA a few years ago LAX-MSP and it was the most uncomfortable coach flight I've had in many years, worse even than United's regular economy (without anyone reclining in front of me, at least), as a 6' tall person. If legroom is important to you, and you can't get comped to a status which will get you at least access to exit rows or you don't book ahead far enough for exit rows to be left around any more, then I doubt you'll enjoy NWA coach if you only like United in Economy Plus (if you are able to get that most of the time).

Also, keep in mind that NWA as such will not be around much longer than a year or so! It just became official last week (after the last approval, from DOJ, came through) that Delta and NWA are merging, and after the merger makes it really one airline then what? (You would at least need to make sure you are just as comfortable with Delta's FF program and Delta's planes, because you don't know whether the combined DL/NW will be more like DL or more like NW in the long run.) So even if it turns out that NWA now has more rows with better seating (something SeatGuru implies), Delta doesn't, and if they shuffle the planes around as the merger progresses, the specific planes NWA flies today could be something you stop being able to depend on.