The jump from Wii to Wii U is the same as from PS2 to PS3, basically. It's not merely a different Wii. There's a lot of great exclusives like Pikmin 3, New Super Mario Bros. U, Super Mario 3D World, Super Smash Bros. for Wii U and Mario Kart 8. You will have to decide for yourself if those games are worth it to you, however.