head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

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

Execution · Pure Mechanics
A late-90s mercenary FPS infamous for its graphic locational damage system.
Half-Life 2 leans Execution (Pure Mechanics); Soldier of Fortune leans Execution (Pure Mechanics).
Soldier of Fortune leans a little harder on execution, though the gap is small.
Half-Life 2
Gravity gun and shooting demand precision.
Soldier of Fortune
Fast twitch aim against fragile enemies decides everything
Soldier of Fortune leans a little harder on reads, though the gap is small.
Half-Life 2
Combine AI scripted, non-adaptive.
Soldier of Fortune
Multiplayer duels add a little human prediction
Soldier of Fortune leans a little harder on variance, though the gap is small.
Half-Life 2
Almost no randomness.
Soldier of Fortune
Campaign layouts and spawns are fixed
Soldier of Fortune leans a little harder on optimization, though the gap is small.
Half-Life 2
Linear progression with no builds.
Soldier of Fortune
Weapon choice and level routes are quickly learned
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.