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
A pure lane-timing reflex test against head-on collision cars.

Execution · Pure Mechanics
Landmark FPS built on physics puzzles and tight gunplay.
Dodge 'Em leans Execution (Pure Mechanics); Half-Life 2 leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Dodge 'Em
Lane-switch timing against closing cars is the whole game
Half-Life 2
Gravity gun and shooting demand precision.
Half-Life 2 leans a little harder on reads, though the gap is small.
Dodge 'Em
Computer cars chase head-on by simple fixed logic
Half-Life 2
Combine AI scripted, non-adaptive.
Dodge 'Em leans a little harder on variance, though the gap is small.
Dodge 'Em
Opposing car spawns vary slightly per loop
Half-Life 2
Almost no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dodge 'Em
Optimal lane patterns are quickly learnable
Half-Life 2
Linear progression with no builds.
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.