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
Aim and spawn memorisation through a fully scripted cinematic campaign.

Execution · Practiced Mastery
Moderate platforming execution through inventive but fixed mental levels.
Call of Duty: Modern Warfare 2 Campaign Remastered leans Execution (Practiced Mastery); Psychonauts 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: Modern Warfare 2 Campaign Remastered
Aim and reaction carry every scripted firefight
Psychonauts
Platforming and psychic combat need moderate precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2 Campaign Remastered
Enemies spawn and behave on fixed scripts
Psychonauts
Mental-world enemies follow fixed behaviours
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2 Campaign Remastered
Set-piece campaign with almost nothing random
Psychonauts
Level layouts are fixed and quickly known
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2 Campaign Remastered
Learning spawns and cover lines trivialises veteran difficulty
Psychonauts
Collectible routing and power upgrades add 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.