head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
Tests twitch aim and physics-prop improvisation against human opponents.

Execution · Pure Mechanics
Fast arena-style shooter mixing a scripted Strogg campaign with twitch multiplayer.
Half-Life 2: Deathmatch leans Execution (Pure Mechanics); Quake 4 leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2: Deathmatch
Aim, movement and gravity-gun catches decide every duel
Quake 4
Aimbot plus strafe-jump inputs dominate both campaign and multiplayer
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2: Deathmatch
Predicting human spawns, dodges and prop throws matters constantly
Quake 4
Multiplayer duels reward predicting human positioning and timing
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2: Deathmatch
Physics props add minor situational chaos
Quake 4
Spawn and item timing add mild uncertainty
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2: Deathmatch
Weapon spawns and map control are learnable layers
Quake 4
Item control routes and weapon picks are learnable
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.