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 · Grand Arena
Fast arena shooter with deep loadout tuning.

Execution · Grand Arena
Team hero shooter blending FPS mechanics with ability economy mind games.
Call of Duty: Modern Warfare III leans Execution (Grand Arena); Overwatch leans Execution (Grand Arena).
Call of Duty: Modern Warfare III leans a little harder on execution, though the gap is small.
Call of Duty: Modern Warfare III
Fast TTK punishes any aim error
Overwatch
Hero aim, movement, and ability timing
Overwatch leans a little harder on reads, though the gap is small.
Call of Duty: Modern Warfare III
Sliding and pre-aim duels reward prediction
Overwatch
Ult tracking, flanks, and baiting human teams
Call of Duty: Modern Warfare III leans a little harder on variance, though the gap is small.
Call of Duty: Modern Warfare III
Spawn flips and map traffic add noise
Overwatch
Minor spread and matchmaking noise
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare III
Loadouts, perks, attachments heavily tuned
Overwatch
Team comps, ult economy, and positioning theory
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.