Having frequently flown VS and BA in the past, I consciously switched to BA-only when they introduced NCW and WT+. Virgin's service is gimmicky, and in my experience their crews don't need encouragement to be cheeky, off-hand, and frequently just plain rude, however much you paid for your ticket.

I switched as the result of a consistent, discernible difference between the two. After several years, the only reason I ever flew VS was 1) the Premium Economy seat (when the other option was BA's Y) and/or 2) the gimmicks in Upper (bars on board, limo transfer). I certainly never went to VS to experience quality service. When BA brought in WT+ and NCW it was a no-brainer.