I've only done VV. I have my first X cruise, 2 weeks from today. I'm eager to see if I like it as much. I thought my VV cruise would be my first and last, but it totally sold me on cruising, and now I'm obsessed.
They seem to constantly be running promotions where $300-$600 worth of alcoholic drinks are included (including right now). I would call the price almost the same as X, when you take into account what's included and what's extra for each, and when these promotions are happening, maybe VV is cheaper (for 2 people).
My only complaint about VV is "not enough trivia" or "not serious enough about trivia". Seems like I'll be happy with the amount on X. Looking forward.