Yes, it varies very much.
Purebreeds are generally very healthy unless they have come from a very bad breeder. Most breeders that I know are terrified of developing a sickly line so any suspect bunny doesn't have babies. Reasonably close breeding also is pretty natural in the rabbit - the social structure of a warren means that father/daughter matings won't be at all rare. I wouldn't advise this as regular practice though without ensuring that unrelated rabbits are put into the "line" regularly, and everyone who I have spoken to does this.
The idea that the flat face in the Nethie causes malocclusion is false - as with any breed some will have it but most won't. The skull is shorter but still lines up. In my experience, the Mini Lop with the worst breed for this.
Certain cross breeds are worth being wary of, those with one ear up and one ear down in particular. The skull is distorted which is what causes the difference. This isn't a problem but should the jaw also be slightly twisted, which is not unusual, then tooh problems can develop. Charles Darwin actually took an interest in this particular point, you can see his illustrations here
http://pages.britishlibrary.net/charles.darwin/texts/variation/variation04.html. He also compares the skeletal structure of lops and normals. If you look carefully at the two sets of skull diagrams you can notice the difference. It is quite interesting if you are of a biological persuation
Also many cross breeds come from people who are not aware of the particulars of breeding rabbits, so whilst you know you are not getting a directly inbred rabbit you are taking a bit of a gamble. For a start, both parents may be highly inbred! :shock: In that case though, it is unlikely that any problematic recessives will be present on both sides.
I don't have anything against either in particular. I have many rabbits myself (about 25) and they are about 50:50 pure bred:cross breed. I also breed the occasional litter of Nethies. Nethies are easy to manage as you are looking at 2-3 babies, 4 absolute max!
I don't post much on many boards, hence why you may not have seen me, but I felt that I could contribute something worthwhile to this thread.
Cat x