Having had severe registered as well as grades-There is really no difference other than a piece of paper. A good horse is a good horse. PERIOD. Only makes a difference if you want to do breed shows, which I did as a kid, with QH, but have to say-not a lot different than doing the regular open circuit. I think that people have gone more toward discipline based shows than they used to, like reining, H/J, eventing, etc. So, in the end, the paper makes no real difference.
As far as health goes-I have no idea who told you that grades were less healthy, but I would challenge that. That is about the silliest thing I have heard in a long time. My feeling is that in some cases they are actually LESS healthy because of inbreeding, much like dogs. A great example is the QH industry, halter horses and HYPP. That is just ONE example.
Buy a horse on its merits. Not for a piece of paper.
Signature undergoing edits. Please standby.......