head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Practiced Mastery
A sci-fi shooter where aim and weapon-switching against scripted alien enemies is the core test.

Execution · Practiced Mastery
Co-op-focused action sequel hurling Titus against Tyranid swarms with parry-heavy melee combat.
Halo: Combat Evolved Anniversary 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.
Halo: Combat Evolved Anniversary
aim and grenade timing carry combat
Warhammer 40,000: Space Marine 2
Parry, dodge and gun-strike timing against swarms
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Combat Evolved Anniversary
covenant AI is scripted, not adaptive
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.
Halo: Combat Evolved Anniversary
enemy spawns and drops vary
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.
Halo: Combat Evolved Anniversary
weapon sandbox and routes are solvable
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.