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
Pioneering rhythm game where a rapping dog believes his way through button-cue raps.

Execution · Pure Mechanics
The full-band rhythm game whose setlist and feel made it the genre's high-water mark.
PaRappa the Rapper leans Execution (Pure Mechanics); Rock Band 2 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.
PaRappa the Rapper
Hitting button cues on beat is the whole game
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.
PaRappa the Rapper
No opponent; teachers follow set lines
Rock Band 2
Charts never respond
PaRappa the Rapper leans a little harder on variance, though the gap is small.
PaRappa the Rapper
Songs are fixed sequences
Rock Band 2
Fixed setlist charts
Rock Band 2 leans a little harder on optimization, though the gap is small.
PaRappa the Rapper
Freestyle scoring quirks for Cool rank
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.