Everything has changed since people posted comments and trip reports here. The scenery, especially, has been extensively revised.
Be nice. <_<
Greg - I've never been on the CZ, but I hear it has the best scenery of any Amtrak route (though I'd argue the Empire Builder could give it a run for the money).
I ride the SWC every year, and it has beautiful scenery as you travel through CO and NM. The Raton Pass and Glorieta Pass are breathtaking. If you're traveling WB, you'll get to see them in daylight. If you're traveling EB, it might be a bit too dark that time of year.
I'm not familiar with the scenery along that route once you get west of Albuquerque, as that's our stopping point, but I've heard very good things about western NM. I believe portions of AZ are in darkness on the WB trip, but I'm not sure about EB. I think others can chime in about that. Most people I talk to on the forum take the SWC between L.A. and Chicago and have more experience with that portion.
Also, I've always received very good service on the SWC. For some reason, I always seem to get the L.A. crew going both directions, and I really like them. Steve usually does the announcements, and he's hilarious, and we had a couple of very good servers in the diner (though I can't recall their names, unfortunately). Our SCAs were Anna Maria and Julio, and they were excellent.