Well I think if you painted a piece of vinyl with Rustoleum and another with SEM you find out what the difference is pretty quick. The paint won't have the flexibility that the SEM does. The gloss level in the SEM is also correct for doing soft interior parts.

One thing I noticed with SEM is a) it takes very little to cover and b) it doesn't change the underlying pattern. It seems to have the absolutely perfect consistency to flow and blend and then dry almost immediately. Even if you have to touch up a spot it blends with no dry area from overspray.