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
Nine pointer-driven minigames bundled with a Wii Remote, from duck-hunt shooting to table tennis.

Execution · Pure Mechanics
Motion-controlled tennis, bowling, golf, baseball and boxing built around simple swing gestures.
Wii Play leans Execution (Pure Mechanics); Wii Sports leans Execution (Pure Mechanics).
Wii Sports leans a little harder on execution, though the gap is small.
Wii Play
Pointer aim and timing carry shooting and ping-pong games
Wii Sports
Motion swing timing and accuracy decide every event
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Wii Play
Two-player duels add slight mutual 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.
Wii Play
Find Mii crowds and target spawns randomise lightly
Wii Sports
Minor physics wobble and CPU behaviour randomness
Wii Sports leans a little harder on optimization, though the gap is small.
Wii Play
Minigames are too shallow to deeply optimise
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.