head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
A fast military shooter where twitch aim against human opponents defines success.

Execution · Pure Mechanics
An arena shooter built on precision aim and power-weapon map control.
Call of Duty: Black Ops 4 leans Execution (Pure Mechanics); Halo Infinite 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: Black Ops 4
aim and reflexes decide most fights
Halo Infinite
Precision aim and strafe duels dominate.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Black Ops 4
predicting human opponents' positioning
Halo Infinite
Adaptive opponents around power weapon timings.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Black Ops 4
battle royale loot is heavily random
Halo Infinite
Spawn flips and weapon drops add 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: Black Ops 4
loadouts and rotations are solvable
Halo Infinite
Map control, weapon timers, and team callouts.
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.