I recently finished a stay in both villa types (3 nights OWV, 2 Reef) and compared the two a few pages up, though technically both were upgraded to a "grand villa". I recommend splitting it the way you have just to get the experience of both. If I was going back a 2nd time I would probably prefer the Reef as it's a bit more private (especially if upgraded to a Grand Reef which has a front facing window) and closer to everything. As far as the move itself, the staff I chatted with remarked that it's a fairly regular occurrence that guests split stays between villa types - they had no issues moving everything for us (even said it wasn't an issue if we left clothes on the hangers). Just to be on the safe side I recommend confirming the timing of the switch when you arrive w/ your concierge (or in advance via email).

Can't go wrong either way, though - enjoy!