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
Cute two-button rhythm game where everything reduces to hitting notes on beat.

Execution · Pure Mechanics
The full-band rhythm game whose setlist and feel made it the genre's high-water mark.
Muse Dash leans Execution (Pure Mechanics); Rock Band 2 leans Execution (Pure Mechanics).
Muse Dash leans a little harder on execution, though the gap is small.
Muse Dash
Two-lane rhythm hits at high BPM are pure hands
Rock Band 2
Guitar, drum, and vocal accuracy on expert charts
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Muse Dash
Charts never adapt
Rock Band 2
Charts never respond
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Muse Dash
Fully deterministic note charts
Rock Band 2
Fixed setlist charts
Rock Band 2 leans a little harder on optimization, though the gap is small.
Muse Dash
Character buffs and chart memorization help margins
Rock Band 2
Overdrive activation paths decide leaderboard scores
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.