I think the point Cal-P was making is less about keeping the 1950s era Budd cars per se, as it was to point out that the single level Heritage-style equipment had many positive attributes. For starters, IMO the P-S and Budd built single level cars rode much more smoothly than the Superliners, and with single level equipment there is always the opportunity to run dome equipment along with the flat tops.

If Amtrak had stuck with single level equipment, any car could in theory be used anywhere in the system, as opposed to what we have now with separate Superliner and Viewliner fleets, not to mention the Talgo and Acela trainsets. There's a lot to be said for keeping it simple.