What's more the Wii offers a choice of three control systems: a standard system using the remote held horizontally or the classic controller; a Wii Sports tennis like system that uses the motion sensitive controller, and a hybrid system that uses the nunchuck to move and the remote to whack the ball. The first isn't all that satisfactory if all you have is the Wii remote, while the latter takes an awful lot of getting used to. The Wii Sports system is great, and will delight any members of your family who are already used to Wii Sports. However, it's not available during the mini-games, so you'll be forced to use the standard configuration instead. The upshot of this is that the Wii version is the better family-friendly party game: just fire up a multiplayer tournament and you're away. However, the 360 version makes for a better single-player experience and gives you the benefit of online play as well.
Looking elsewhere I note that a lot of people have been fairly grumpy about Sega Superstars Tennis, mostly because they feel it compares poorly to Virtua Tennis 3 as a single player game. For me, that's a bit of a non-issue - compare it to other family sports games and it's well ahead of the pack. Give me a choice between this and Sonic and Mario at the Olympic Games and I know which one I'd rather play. More importantly, it's the sort of game that I'd happily recommend to anyone who wants a game they can enjoy with the family while still have something worth playing on their own, and a must for anyone who's looking for a more feature-packed alternative to the tennis game in Wii Sports. If that means you, then buy away. It's not quite as addictive or rewarding long-term as VT3, but Sega is still serving aces when it comes to family-friendly fun.
Don't expect the depth of Virtua Tennis 3 and you'll find one of the best family sports games around. Thoroughly enjoyable and a must for anyone with rose-tinted memories of the Dreamcast years.