Well, I'd like to start off by saying they are both excellent multiplayer mini-games. Both are great for a party. I'm sure you'd be happy with both. I'll give you some ideas of which one you might want to choose:
- The 8th in the series of a very sucsesful franchise.
- Features Nintendo characters from Mushroom Kingdom.
- Amazing creativity and gameplay.
- Features Wario and Miis
- Over 200 mini-games
- Excellent use of the Wii Remote.
Out of both, I would say MP 8 but it's up to you really.