head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
A 3D marble-rolling platformer through skyborne courses.

Execution · Pure Mechanics
A classic beat-em-up demanding execution against scripted enemy waves.
Marble Skies leans Execution (Pure Mechanics); Teenage Mutant Ninja Turtles III: The Manhattan Project 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.
Marble Skies
precise marble control through 3D courses
Teenage Mutant Ninja Turtles III: The Manhattan Project
beat-em-up timing and enemy juggling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Marble Skies
no opponent, solo time-trial platforming
Teenage Mutant Ninja Turtles III: The Manhattan Project
enemies run simple fixed scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Marble Skies
fixed level layouts, minimal randomness
Teenage Mutant Ninja Turtles III: The Manhattan Project
minor enemy spawn randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Marble Skies
route memorization for best times
Teenage Mutant Ninja Turtles III: The Manhattan Project
character choice and route memorization
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.