I have used Hoya Pro 1 Super multicoated and B+W MRC and see no significant difference either way. I do see a difference using the cheap Hoya.
If testing one against the other then one really needs to shoot in identical conditions, and the examples above are clearly shot under very different conditions, and using comparable priced items - I don't know if that was the case above or whether the Hoya was a cheapo.
The UV's I use in harsh conditions are all B+W MRC but as the Pro 1 is quite a bit cheaper and gives me the same discernable performance I use the Hoya CP's.
I like the B&W ones purely because the MRC ones seem easy to clean.
It could just be me, but whenever I try to clean a Hoya I tend to mess them up, once they get a bit manky they are a ***** to clean - I've stripped a coating from one using Eclipse fluid to clean (my fault there).
The MRC's come up as good a new with a polish I find. Ditto with Heliopan. Same glass / coatings as B&W.
Not convinced there is a difference optically though. All filters are over-priced for what they are IMHO.