This.
Before I knew better, I bought my German Shepherd Dog, who was supposed to be pure bred and superior. Six months on, we learn she has double hip dyplasia. So yeah. They aren't "better" and you "don't know what you're getting." My mutts? They are just fine. So that whole theory? A load of codswallop.
She died just before her 13th birthday a few years back, but she was totally disabled her whole life.