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 · Practiced Mastery
The original 2003 WWII shooter built around cinematic squad set pieces.

Execution · Practiced Mastery
Co-op-focused action sequel hurling Titus against Tyranid swarms with parry-heavy melee combat.
Call of Duty leans Execution (Practiced Mastery); Warhammer 40,000: Space Marine 2 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
Aim and reaction carry the scripted firefights
Warhammer 40,000: Space Marine 2
Parry, dodge and gun-strike timing against swarms
Call of Duty leans a little harder on reads, though the gap is small.
Call of Duty
Light multiplayer prediction; campaign AI is scripted
Warhammer 40,000: Space Marine 2
PvP Eternal War adds some human prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Some spawn and hit unpredictability
Warhammer 40,000: Space Marine 2
Tyranid swarm spawns vary run to run
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Memorising set pieces and weapon positions
Warhammer 40,000: Space Marine 2
Class builds and perk loadouts reward 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.