head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Pure Mechanics
WWII gunfight execution with light multiplayer prediction.

Execution · Practiced Mastery
FPS aim welded to a team economy of base-destruction priorities.
Call of Duty 3 leans Execution (Pure Mechanics); Command & Conquer: Renegade 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
Command & Conquer: Renegade
FPS aim in infantry and vehicle fights 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
Command & Conquer: Renegade
Multiplayer base assaults involve predicting human team pushes
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
Command & Conquer: Renegade
Maps and economy rules are fully known
Command & Conquer: Renegade leans a little harder on optimization, though the gap is small.
Call of Duty 3
Map knowledge and weapon choice reward light study
Command & Conquer: Renegade
Credit economy and building-target priority decide C&C-mode matches
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.