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
Spectacle hack-and-slash where reflexes and combo flow drive every fight.

Execution · Pure Mechanics
A crossover Olympic sports collection where waggle timing and mashing form set the podium.
God of War III leans Execution (Pure Mechanics); Mario & Sonic at the Olympic Games 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.
God of War III
Combo execution and QTE timing carry combat.
Mario & Sonic at the Olympic Games
Motion timing and mashing rhythm decide event results
Mario & Sonic at the Olympic Games leans a little harder on reads, though the gap is small.
God of War III
Bosses fully scripted spectacle.
Mario & Sonic at the Olympic Games
Human rivals race in parallel; little interaction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
God of War III
Almost no randomness.
Mario & Sonic at the Olympic Games
Events are fixed; almost no randomness
God of War III leans a little harder on optimization, though the gap is small.
God of War III
Upgrade paths short and obvious.
Mario & Sonic at the Olympic Games
Learning each event's optimal technique caps quickly
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.