What's your budget and how long do you think you'll own it?
For approximately $4000 or so, you can have the Coachmen roof re-done with Rhino Liner. I think it would outlast the coach.
Although I'd live with the membrane roof, myself. Heck, I made a small tear in one on my fiver with a tree branch. I patched it with Eternabond tape and went on my way. In the scheme of things, it's an unlikely event and easily dealt with. Now, the water leak in Leprechauns, that would concern me. If you can satisfy yourself that they have solved the problem on new builds coming out of the factory today, go for it.
There aren't that many brands of C's, really.
