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
WWII gunfight execution with light multiplayer prediction.

Execution · Competitive PvP
A soccer game testing passing timing and anticipation against opposing players.
Call of Duty 3 leans Execution (Pure Mechanics); Ultimate Soccer leans Execution (Competitive PvP).
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
Ultimate Soccer
Passing and shot timing demand moderate control
Ultimate Soccer leans a little harder on reads, though the gap is small.
Call of Duty 3
Multiplayer adds modest human positional prediction
Ultimate Soccer
Versus humans, anticipating passes and runs matters
Ultimate Soccer leans a little harder on variance, though the gap is small.
Call of Duty 3
Scripted setpieces and spawn flow add minor unknowns
Ultimate Soccer
Deflections and keeper saves add chance
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
Ultimate Soccer
Formation and passing-strategy choices carry light planning
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.