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

Execution · Pure Mechanics
Classic arena aim married to champion abilities, tested against adaptive human opponents in fast duel maps.

Execution · Pure Mechanics
Pure aim and movement skill tested against adaptive human opponents competing for spawn-cycle dominance.
Quake Champions leans Execution (Pure Mechanics); Quake III Arena 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.
Quake Champions
Champion abilities add execution layers on top of classic rail and rocket aim
Quake III Arena
Rail and rocket aim at speed is the entire game
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Quake Champions
Human duels require reading opponent ability usage and positioning
Quake III Arena
Human opponents adapt their routes and timings in direct response
Quake Champions leans a little harder on variance, though the gap is small.
Quake Champions
Ability cooldowns introduce mild timing uncertainty per match
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.
Quake Champions
Champion matchup knowledge and item timing are solvable advantages
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.