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
WWII gunfight execution with light multiplayer prediction.

Execution · Pure Mechanics
Squad shooting against scripted hordes with light class-loadout decisions.
Call of Duty 3 leans Execution (Pure Mechanics); Resident Evil: Operation Raccoon City 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 3
Aimbot trivialises both campaign and multiplayer gunfights
Resident Evil: Operation Raccoon City
Third-person aim against zombie and soldier swarms carries the game
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Multiplayer adds modest human positional prediction
Resident Evil: Operation Raccoon City
Versus modes add human prediction; campaign AI is scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Scripted setpieces and spawn flow add minor unknowns
Resident Evil: Operation Raccoon City
Infection mechanics and spawn chaos add mild unpredictability
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Map knowledge and weapon choice reward light study
Resident Evil: Operation Raccoon City
Class abilities and loadouts are a shallow solvable layer
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.