head to head
S.C.A.T.: Special Cybernetic Attack Team asks more than Half-Life 2, and the gap is execution.

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

Execution · Pure Mechanics
A punishing NES run-and-gun testing dodge execution over memorised enemy waves.
Half-Life 2 leans Execution (Pure Mechanics); S.C.A.T.: Special Cybernetic Attack Team leans Execution (Pure Mechanics).
S.C.A.T.: Special Cybernetic Attack Team leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
S.C.A.T.: Special Cybernetic Attack Team
Dodging dense fire while managing floating aim is everything
Half-Life 2 leans a little harder on reads, though the gap is small.
Half-Life 2
Combine AI scripted, non-adaptive.
S.C.A.T.: Special Cybernetic Attack Team
Alien waves are identical every playthrough
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.
S.C.A.T.: Special Cybernetic Attack Team
Fixed spawns - nothing hidden after one run
S.C.A.T.: Special Cybernetic Attack Team leans clearly harder on optimization.
Half-Life 2
Linear progression with no builds.
S.C.A.T.: Special Cybernetic Attack Team
Memorising stage layouts and satellite positioning enables clears
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.