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

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

Execution · Pure Mechanics
A rhythm game testing precise timing while drumming along to song charts.
Guitar Hero II leans Execution (Pure Mechanics); Taiko no Tatsujin: The Drum Master! 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
Taiko no Tatsujin: The Drum Master!
Precise rhythmic timing on every note is everything
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
Taiko no Tatsujin: The Drum Master!
Solo rhythm game with no opponent to predict
Taiko no Tatsujin: The Drum Master! leans a little harder on variance, though the gap is small.
Guitar Hero II
Fully deterministic charts
Taiko no Tatsujin: The Drum Master!
Note charts are fixed, no randomness
Taiko no Tatsujin: The Drum Master! leans a little harder on optimization, though the gap is small.
Guitar Hero II
Star power pathing for leaderboard play
Taiko no Tatsujin: The Drum Master!
Some scoring strategy but timing dominates
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.