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

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

Execution · Pure Mechanics
Tests twitch aim and physics-prop improvisation against human opponents.
Half-Life 2 leans Execution (Pure Mechanics); Half-Life 2: Deathmatch leans Execution (Pure Mechanics).
Half-Life 2: Deathmatch leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
Half-Life 2: Deathmatch
Aim, movement and gravity-gun catches decide every duel
Half-Life 2: Deathmatch leans clearly harder on reads.
Half-Life 2
Combine AI scripted, non-adaptive.
Half-Life 2: Deathmatch
Predicting human spawns, dodges and prop throws matters constantly
Half-Life 2: Deathmatch leans a little harder on variance, though the gap is small.
Half-Life 2
Almost no randomness.
Half-Life 2: Deathmatch
Physics props add minor situational chaos
Half-Life 2: Deathmatch leans a little harder on optimization, though the gap is small.
Half-Life 2
Linear progression with no builds.
Half-Life 2: Deathmatch
Weapon spawns and map control are learnable layers
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.