Honestly, in my experience, there's no real difference in health between furred and naked rats. I've had perfectly healthy hairless/double rex rats that lived a good life, and I've had furred rats who haven't.
I'll agree, although I've found that my hairless are much more prone to 'rat acne' (as I call it) and eye infections than my hairy ones. Also they seem to get chest infections a little more than the hairy's. But, I've not had one so far that has had serious problems, aka tumours, inner ear infections, strokes, like my hairys have.
I just wondered if anyone had noticed anything similar. Must just be my odd bunch! Lol