I needed to lose a lot of weight, plus there are a few games which needed the Balance Board (although I bought that separately) — so, combining the need for weight loss with a Balance Board … Wii Fit U seemed natural.
Actually, it's the Fit Meter that's most interesting: being able to measure your activity when you're not busy training is the thing that will help keep your motivation up. Just clip it to your belt, and let it count. Couldn't be simpler!
So you both have the solid set of activities and games from the previous Wii Fit titles, plus mtivation to keep you on track when you're not in front of the TV. What's not to like-