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
Trilogy capstone whose equal-start arena multiplayer defined a console generation.

Execution · Competitive PvP
Tests stylish movement-shooter mechanics against human teams in objective modes.
Halo 3 leans Execution (Pure Mechanics); S4 League leans Execution (Competitive PvP).
Halo 3 leans a little harder on execution, though the gap is small.
Halo 3
Precision aim and grenade-melee timing
S4 League
Wall-running movement and aim duels decide exchanges
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Halo 3
Equal-start fights reward predicting humans
S4 League
Human opponents in Touchdown demand constant prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Halo 3
Equipment pickups and spawn variation
S4 League
Some weapon spread and mode chaos
Halo 3 leans a little harder on optimization, though the gap is small.
Halo 3
Power-weapon timers and map control
S4 League
Loadout choices and map knowledge matter underneath
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.