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 · Pure Mechanics
Linear military FPS about resisting an occupation of the United States.
Half-Life 2 leans Execution (Pure Mechanics); Homefront 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.
Half-Life 2
Gravity gun and shooting demand precision.
Homefront
Standard shooter gunplay carries the campaign
Homefront leans a little harder on reads, though the gap is small.
Half-Life 2
Combine AI scripted, non-adaptive.
Homefront
Multiplayer adds some human prediction
Homefront leans a little harder on variance, though the gap is small.
Half-Life 2
Almost no randomness.
Homefront
Scripted setpieces, little randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2
Linear progression with no builds.
Homefront
Modest loadout and map knowledge layer
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.