Neither is objectively "better" — they serve different needs:
Pros: Motion controls (innovative), family-friendly, great party games (Wii Sports, Mario Kart), affordable.
Cons: Limited library vs. competitors, motion imprecision, lower graphics.
Pros: Dual screens + touchscreen (unique gameplay), portable, diverse genres (RPG, puzzle, action), massive library.
Cons: Lower processing power, limited online, touchscreen can be finicky.
Research specific game libraries for each to decide.