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 · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.

Execution · Competitive PvP
A fast-paced online football game emphasizing mechanical ball control and outplaying opposing players.
Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP); Rematch leans Execution (Competitive PvP).
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
Fast time-to-kill rewards raw aim and reflex
Rematch
tight ball control, shooting, and movement skill
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
Outguessing human rotations and flanks
Rematch
reading human opponents' positioning and passing lanes
Call of Duty: Modern Warfare 2 leans a little harder on variance, though the gap is small.
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
Rematch
ball physics bounces add minor unpredictability
Call of Duty: Modern Warfare 2 leans a little harder on optimization, though the gap is small.
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
Rematch
team formations and tactics are learnable
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.