head to head
Neither is simply harder - they are hard in different places. osu! demands more execution; Super Mario World demands more optimization.

Execution · Pure Mechanics
Rhythm game where clicking circles to the beat becomes an athletic discipline.

Execution · Pure Mechanics
Precise jump execution across fixed levels with secrets to memorise.
osu! leans Execution (Pure Mechanics); Super Mario World leans Execution (Pure Mechanics).
osu! leans clearly harder on execution.
osu!
Pixel-perfect cursor aim and tapping at extreme speeds
Super Mario World
Perfect inputs trivialise every jump, spin and cape flight
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
osu!
No opponent interaction in scoring
Super Mario World
Scripted Koopas adapt to nothing
Super Mario World leans a little harder on variance, though the gap is small.
osu!
Beatmaps are fully deterministic
Super Mario World
Levels are fixed; nothing hidden survives one playthrough
Super Mario World leans clearly harder on optimization.
osu!
Mod choices and map selection for ranking
Super Mario World
Secret exits and route knowledge add a modest solvable layer
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.