These were both in my work garage. Imagine yourself taking one for a long road trip. Very different ways to do the same thing.
BTW, the Roadmaster wasn’t perfect, but was uber clean in and out. No rust with a leather interior that looked like it was sourced from Lazyboy. I could sleep all the way through the Appalachians in that back seat. The SL550 had brown leather interior. Great if you don’t have kids.