I just came from Phoenix to Atlanta on I-20...OK, I-10 first and then 20. I was impressed with how good I-20 is over I-40 that I usually use. Some rough pavement (fairly smooth but rough surface texture) on I-10 just before New Mex but excellent concrete in west TX. Again some rough pavement before Shreveport and very little construction on the entire route.
I would say 40 is more scenic but you have more climbs where 10/20 is almost flat and after Dallas is not very scenic unless you like the desert and 100 mile views if no dust storms.