No doubt there will be other opinions, but Phill I can tell you that one thing about the RM: they are not consistent. By that I mean that there seem to be some sets that are well and thoughtfully put together by them as VIP, but others seemingly original that are not as of good a quality.
Then there is each individual coin, wherein factors such as how early on in the life of a die it was struck and if a particular specimen was given just a bit more care by the operators. Also, no doubt coins that may have been intended as VIP may have found their way into "ordinary" sets.
I have talked with my good friend Steve H. many times in the past about such phenomena as RM proofs of silver and copper 20th C. are a focus of mine, and we (if I may speak for him) are of the opinion that it is not always possible to differentiate on individual merit alone if a particular coin is an ordinary proof or a VIP proof particularly if a specimen that may be the former is of early and good strike with plenty of extra field reflectivity, milling crispness and frosted devices; the latter phenomenon is referred to by some as DMPL, or deep mirror proof like.
This may represent a buying opportunity as individual coins come up that are under appreciated as to their quality. A related problem however is that many of the crowns in particular are actually these DMPL coins that are slabbed and sold as VIP, when they may not be. I would caution against paying fancy prices for these.
BTW, I personally do not like the term "VIP", and perhaps it is the liberal in me...