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 space-faring Call of Duty mixing jetpack multiplayer with a starfighter campaign.

Execution · Pure Mechanics
Trilogy capstone whose equal-start arena multiplayer defined a console generation.
Call of Duty: Infinite Warfare leans Execution (Pure Mechanics); Halo 3 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.
Call of Duty: Infinite Warfare
Wall-running and thrust jumps demand mechanical skill
Halo 3
Precision aim and grenade-melee timing
Halo 3 leans a little harder on reads, though the gap is small.
Call of Duty: Infinite Warfare
Human opponents reward movement prediction
Halo 3
Equal-start fights reward predicting humans
Call of Duty: Infinite Warfare leans a little harder on variance, though the gap is small.
Call of Duty: Infinite Warfare
Spawn logic and lobby variance add noise
Halo 3
Equipment pickups and spawn variation
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Infinite Warfare
Rig choice and movement routes are solvable
Halo 3
Power-weapon timers and map control
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.