In theory, the MRs are better. But it sounds as though most of the construction of both series is the same, with both reflecting the results of ClarityCap's research on reducing vibrations. The benefits of the MR sounded pretty limited to me, but what do I know...
In any case, Madisound won't carry the ESA 630V going forward, so this is a great chance to pick up some of those caps.
Best regards,
Adam