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
Precise jump execution across fixed levels with secrets to memorise.

Execution · Pure Mechanics
Classic Tetris execution under audiovisual flow, speed still decides everything.
Super Mario World leans Execution (Pure Mechanics); Tetris Effect leans Execution (Pure Mechanics).
Tetris Effect leans a little harder on execution, though the gap is small.
Super Mario World
Perfect inputs trivialise every jump, spin and cape flight
Tetris Effect
Piece placement under speed and Zone timing is the whole test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Super Mario World
Scripted Koopas adapt to nothing
Tetris Effect
Solo experience with no opponent to model
Tetris Effect leans a little harder on variance, though the gap is small.
Super Mario World
Levels are fixed; nothing hidden survives one playthrough
Tetris Effect
Randomised bag is bounded and quickly mappable
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Super Mario World
Secret exits and route knowledge add a modest solvable layer
Tetris Effect
Stacking theory and Zone usage have known optimal lines
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.