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
High-speed trick execution along optimised lines down fixed mountains.

Execution · Pure Mechanics
Precise jump execution across fixed levels with secrets to memorise.
SSX leans Execution (Pure Mechanics); Super Mario World leans Execution (Pure Mechanics).
SSX leans a little harder on execution, though the gap is small.
SSX
Trick timing, landings and line control at speed are everything
Super Mario World
Perfect inputs trivialise every jump, spin and cape flight
SSX leans a little harder on reads, though the gap is small.
SSX
Rival AI racers are aggressive but mappable
Super Mario World
Scripted Koopas adapt to nothing
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
SSX
Courses are fixed once learned
Super Mario World
Levels are fixed; nothing hidden survives one playthrough
SSX leans a little harder on optimization, though the gap is small.
SSX
Optimal trick lines and shortcut routing maximise score
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.