head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

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

Execution · Pure Mechanics
Pure aim and movement skill tested against adaptive human opponents competing for spawn-cycle dominance.
Dirty Bomb leans Execution (Pure Mechanics); Quake III Arena leans Execution (Pure Mechanics).
Quake III Arena leans a little harder on execution, though the gap is small.
Dirty Bomb
Fast strafing gunfights and ability timing need quick hands
Quake III Arena
Rail and rocket aim at speed is the entire game
Quake III Arena leans a little harder on reads, though the gap is small.
Dirty Bomb
Human teams adapt pushes around objective chokepoints
Quake III Arena
Human opponents adapt their routes and timings in direct response
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dirty Bomb
Fixed maps and abilities, minor loadout-card randomness
Quake III Arena
Spawn locations have mild randomness but are quickly mapped
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dirty Bomb
Merc compositions and objective timings reward planning
Quake III Arena
Armor and weapon timing routes are learnable and highly leveraged
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.