In service terms, I would suggest First is streets ahead of Virgin Upper Class but then they are completely different products...First is also considerably more expensive and exclusive.
If I had the choice, BA First every time.
The real decision comes when comparing Club with UC. For my money, 747 Upper Deck BA Club (seat 64K or 64A) beats VS Upper Class. On a 777, possibly VS has the edge if you consider the Clubhouse at T3..until you get bored with it.
All very subjective of course....