In the case of Labo, Nintendo has made something that uses a gaming console in ways you'd never have expected. It turns your Switch into a toy. Do I wish that toy had a bit more depth to it? Sure, but the simple act of creating those toys is quite enough to make Labo something special.
Meanwhile Wii Fit U's mini-games are fun, but still suffer from being single-player/non-simultaneous multiplayer and there just isn't that much new stuff. If you're looking for something that will keep you motivated and get you moving, it could definitely work and the Fit Meter is an extra level of motivation, but if Wii Fit didn't do it before then I'm not sure it will work for you now. The good part is that the game is free until the end of the month so you can find out for yourself.