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 · Practiced Mastery
Timing-based grapple execution with light opponent prediction in multiplayer matches.

Execution · Pure Mechanics
Motion-controlled tennis, bowling, golf, baseball and boxing built around simple swing gestures.
WCW Mayhem leans Execution (Practiced Mastery); 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.
WCW Mayhem
Timing grapples, reversals and strikes decides every match
Wii Sports
Motion swing timing and accuracy decide every event
WCW Mayhem leans a little harder on reads, though the gap is small.
WCW Mayhem
Human opponents in versus add a modest prediction layer
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.
WCW Mayhem
Weapon spawns and AI behaviour add minor noise
Wii Sports
Minor physics wobble and CPU behaviour randomness
WCW Mayhem leans a little harder on optimization, though the gap is small.
WCW Mayhem
Learning move lists and match-type quirks is a fixed problem
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.