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 · Practiced Mastery
Frozen-planet shooter about managing heat while gunning down giant bugs.
Call of Duty 3 leans Execution (Pure Mechanics); Lost Planet: Extreme Condition leans Execution (Practiced Mastery).
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
Lost Planet: Extreme Condition
Grapple movement and Akrid weak-point shooting
Call of Duty 3 leans a little harder on reads, though the gap is small.
Call of Duty 3
Multiplayer adds modest human positional prediction
Lost Planet: Extreme Condition
Multiplayer modes add some mind games
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
Lost Planet: Extreme Condition
Campaign encounters are fixed
Lost Planet: Extreme Condition leans a little harder on optimization, though the gap is small.
Call of Duty 3
Map knowledge and weapon choice reward light study
Lost Planet: Extreme Condition
Thermal energy management and boss weak points
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.