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

Execution · Pure Mechanics
Sequel rhythm game with harder setlists and refined plastic-guitar technique.

Execution · Pure Mechanics
Cute two-button rhythm game where everything reduces to hitting notes on beat.
Guitar Hero II leans Execution (Pure Mechanics); Muse Dash 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.
Guitar Hero II
Harder charts, hammer-ons, and three-note chords
Muse Dash
Two-lane rhythm hits at high BPM are pure hands
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
Muse Dash
Charts never adapt
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Guitar Hero II
Fully deterministic charts
Muse Dash
Fully deterministic note charts
Muse Dash leans a little harder on optimization, though the gap is small.
Guitar Hero II
Star power pathing for leaderboard play
Muse Dash
Character buffs and chart memorization help margins
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.