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 · Pure Mechanics
WWII gunfight execution with light multiplayer prediction.

Execution · Pure Mechanics
An early top-down shootout game testing precise aim against a human opponent.
Call of Duty 3 leans Execution (Pure Mechanics); Outlaw leans Execution (Pure Mechanics).
Outlaw leans a little harder on execution, though the gap is small.
Call of Duty 3
Aimbot trivialises both campaign and multiplayer gunfights
Outlaw
precise aiming and movement in duels
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
Outlaw
human opponents adapt dueling tactics
Call of Duty 3 leans a little harder on variance, though the gap is small.
Call of Duty 3
Scripted setpieces and spawn flow add minor unknowns
Outlaw
minimal randomness in shootouts
Call of Duty 3 leans a little harder on optimization, though the gap is small.
Call of Duty 3
Map knowledge and weapon choice reward light study
Outlaw
minimal system depth
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.