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
An open-source rhythm battler whose rap-duel format spawned a massive modding scene.

Execution · Pure Mechanics
Sequel rhythm game with harder setlists and refined plastic-guitar technique.
Friday Night Funkin' leans Execution (Pure Mechanics); Guitar Hero II leans Execution (Pure Mechanics).
Guitar Hero II leans a little harder on execution, though the gap is small.
Friday Night Funkin'
Four-key arrow streams get genuinely fast on hard
Guitar Hero II
Harder charts, hammer-ons, and three-note chords
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Friday Night Funkin'
Opponents sing scripted patterns
Guitar Hero II
Static note highways
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Friday Night Funkin'
Charts fully deterministic
Guitar Hero II
Fully deterministic charts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Friday Night Funkin'
Chart memorization for full combos
Guitar Hero II
Star power pathing for leaderboard play
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.