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
A vibrant 2D platformer with rhythm-based highlight levels.

Execution · Pure Mechanics
The full-band rhythm game whose setlist and feel made it the genre's high-water mark.
Rayman Legends leans Execution (Pure Mechanics); Rock Band 2 leans Execution (Pure Mechanics).
Rock Band 2 leans a little harder on execution, though the gap is small.
Rayman Legends
Tight 2D platforming and music levels
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.
Rayman Legends
No adaptive opponent
Rock Band 2
Charts never respond
Rayman Legends leans a little harder on variance, though the gap is small.
Rayman Legends
Fixed levels
Rock Band 2
Fixed setlist charts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Rayman Legends
Time trial routing
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.