head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

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

Execution · Pure Mechanics
DS stylus rhythm game where a male cheer squad saves lives through perfectly timed taps.
Guitar Hero II leans Execution (Pure Mechanics); Osu! Tatakae! Ouendan 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
Osu! Tatakae! Ouendan
Stylus tap, drag, and spin precision at high tempo
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
Osu! Tatakae! Ouendan
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
Osu! Tatakae! Ouendan
Fully fixed note placements
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
Osu! Tatakae! Ouendan
Memorizing layouts matters less than stylus accuracy
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.