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

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

Execution · Pure Mechanics
Motion-controlled tennis, bowling, golf, baseball and boxing built around simple swing gestures.
Kinect Sports: Season Two leans Execution (Pure Mechanics); Wii Sports leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Kinect Sports: Season Two
Full-body motion timing is the entire skill surface
Wii Sports
Motion swing timing and accuracy decide every event
Wii Sports leans a little harder on reads, though the gap is small.
Kinect Sports: Season Two
Party opponents barely reward prediction
Wii Sports
Casual local opponents add light mind games
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 Sports
Minor physics wobble and CPU behaviour randomness
Wii Sports leans a little harder on optimization, though the gap is small.
Kinect Sports: Season Two
Minigames have little system depth to solve
Wii Sports
Simple technique tricks like bowling spin are learnable
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.