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
Sequel rhythm game with harder setlists and refined plastic-guitar technique.

Execution · Pure Mechanics
A fast arcade rail-shooter testing reflexes through surreal scrolling stages.
Guitar Hero II leans Execution (Pure Mechanics); Space Harrier II leans Execution (Pure Mechanics).
Guitar Hero II leans a little harder on execution, though the gap is small.
Guitar Hero II
Harder charts, hammer-ons, and three-note chords
Space Harrier II
reflex dodging in fast rail-shooter
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Guitar Hero II
Static note highways
Space Harrier II
fixed enemy patterns, no adaptation
Space Harrier II leans a little harder on variance, though the gap is small.
Guitar Hero II
Fully deterministic charts
Space Harrier II
minimal randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Guitar Hero II
Star power pathing for leaderboard play
Space Harrier II
little beyond memorizing enemy waves
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.