head to head
Unreal Tournament 2003 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
A fast arena shooter where twitch aim and movement against human opponents is everything.
Half-Life 2 leans Execution (Pure Mechanics); Unreal Tournament 2003 leans Execution (Pure Mechanics).
Unreal Tournament 2003 leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
Unreal Tournament 2003
aim and movement speed decide duels
Unreal Tournament 2003 leans clearly harder on reads.
Half-Life 2
Combine AI scripted, non-adaptive.
Unreal Tournament 2003
predicting human opponent positioning
Unreal Tournament 2003 leans a little harder on variance, though the gap is small.
Half-Life 2
Almost no randomness.
Unreal Tournament 2003
weapon and pickup spawns vary
Unreal Tournament 2003 leans a little harder on optimization, though the gap is small.
Half-Life 2
Linear progression with no builds.
Unreal Tournament 2003
map control and item timing solvable
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.