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 · Practiced Mastery
Tests shooter mechanics fused with real-time base-building economy against human teams.
Halo 3 leans Execution (Pure Mechanics); Starhawk leans Execution (Practiced Mastery).
Halo 3 leans a little harder on execution, though the gap is small.
Halo 3
Precision aim and grenade-melee timing
Starhawk
Vehicle dogfights and third-person gunplay demand twitch skill
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
Starhawk
Predicting enemy build placement and pushes matters online
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
Starhawk
Little hidden beyond fog of incoming drops
Starhawk leans a little harder on optimization, though the gap is small.
Halo 3
Power-weapon timers and map control
Starhawk
Rift economy and build-and-battle structure placement decide matches
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.