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 rhythm racer that turns any music file into a reflex puzzle track.

Execution · Practiced Mastery
A stylish call-and-response rhythm adventure where reporter Ulala dances to save the galaxy.
Audiosurf leans Execution (Pure Mechanics); Space Channel 5: Part 2 leans Execution (Practiced Mastery).
Audiosurf leans a little harder on execution, though the gap is small.
Audiosurf
Lane-switching to the beat tests reaction speed.
Space Channel 5: Part 2
Precise timing on call-and-response button sequences
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Audiosurf
No opponent.
Space Channel 5: Part 2
Sequences are scripted
Audiosurf leans a little harder on variance, though the gap is small.
Audiosurf
Track generated from song, then fixed.
Space Channel 5: Part 2
First playthrough hides upcoming commands
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Audiosurf
Block-matching color strategy learnable per song.
Space Channel 5: Part 2
Memorizing every routine for perfect runs
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.