head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Pure Mechanics
A motion-control party collection testing full-body timing and little else.

Execution · Pure Mechanics
Nine pointer-driven minigames bundled with a Wii Remote, from duck-hunt shooting to table tennis.
Kinect Sports: Season Two leans Execution (Pure Mechanics); Wii Play leans Execution (Pure Mechanics).
Kinect Sports: Season Two leans a little harder on execution, though the gap is small.
Kinect Sports: Season Two
Full-body motion timing is the entire skill surface
Wii Play
Pointer aim and timing carry shooting and ping-pong games
Wii Play leans a little harder on reads, though the gap is small.
Kinect Sports: Season Two
Party opponents barely reward prediction
Wii Play
Two-player duels add slight mutual prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Kinect Sports: Season Two
Sensor reading adds unintended noise
Wii Play
Find Mii crowds and target spawns randomise lightly
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Kinect Sports: Season Two
Minigames have little system depth to solve
Wii Play
Minigames are too shallow to deeply optimise
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.