I’d like to think that at least one of everything could have been preserved. Wishful thinking I know ,but if only someone had thought to buy one of the early diesels instead of yet another 8F. Instead we have multiples of several classes but none of others. Many DMUs look very similar but loads have preserved.
However the fundamental difference between DMUs and EMUs is one are a viable prospect for pretty much any Heritage Railway to use - whereas the other isn't.