Prefer PPG DCC
Well,
I've built two RV's now and I've done this both ways. My '9 has about 6 years and 500 hours on a Rustoleum interior. There are significant wear areas on the roll bar and other areas that get contact. The surface finish is also just okay, not great.
My '8 I shot high gloss WHITE PPG DCC which is a single stage urethane. This is really a very tough paint and I like it a lot. For all you folks that just know that it will reflect, sorry, but its a non-issue. The panel is even white and no problems there. Since all of this area is below the canopy it just doesn't get a chance to reflect up into the plex.
This boils down to what you want to achieve. If you want easy and cheap, go rattle can knowing thats its a second class finish. If you want a MUCH tougher, higher quality finish, and don't mind a little bit of work, then shoot a good quality urethane.