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 · Pure Mechanics
Landmark FPS built on physics puzzles and tight gunplay.

Execution · Practiced Mastery
A Serious Sam-style horde shooter testing strafing aim against scripted waves.
Half-Life 2 leans Execution (Pure Mechanics); Will Rock 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.
Half-Life 2
Gravity gun and shooting demand precision.
Will Rock
Circle-strafing huge enemy swarms is the whole test
Half-Life 2 leans a little harder on reads, though the gap is small.
Half-Life 2
Combine AI scripted, non-adaptive.
Will Rock
Monsters charge in fixed spawned waves
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2
Almost no randomness.
Will Rock
Spawns are scripted and repeat identically
Will Rock leans a little harder on optimization, though the gap is small.
Half-Life 2
Linear progression with no builds.
Will Rock
Weapon choice and arena positioning 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.