head to head
Dirty Bomb asks more than Half-Life 2, and the gap is reads.

Execution · Pure Mechanics
Free-to-play objective shooter from Splash Damage with mercenary classes.

Execution · Pure Mechanics
Landmark FPS built on physics puzzles and tight gunplay.
Dirty Bomb leans Execution (Pure Mechanics); Half-Life 2 leans Execution (Pure Mechanics).
Dirty Bomb leans clearly harder on execution.
Dirty Bomb
Fast strafing gunfights and ability timing need quick hands
Half-Life 2
Gravity gun and shooting demand precision.
Dirty Bomb leans clearly harder on reads.
Dirty Bomb
Human teams adapt pushes around objective chokepoints
Half-Life 2
Combine AI scripted, non-adaptive.
Dirty Bomb leans a little harder on variance, though the gap is small.
Dirty Bomb
Fixed maps and abilities, minor loadout-card randomness
Half-Life 2
Almost no randomness.
Dirty Bomb leans clearly harder on optimization.
Dirty Bomb
Merc compositions and objective timings reward planning
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.