head to head
Neither is simply harder - they are hard in different places. Millipede demands more variance; Super Mario Odyssey demands more optimization.

Execution · Pure Mechanics
Raw arcade reflexes against accelerating swarms with mild spawn randomness.

Execution · Pure Mechanics
A 3D platformer whose joy lives in tight movement and capture-driven traversal.
Millipede leans Execution (Pure Mechanics); Super Mario Odyssey 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.
Millipede
Trackball precision under swarming pressure is everything
Super Mario Odyssey
Precise platforming and capture-move tech ceiling.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Millipede
Enemies follow fixed movement rules
Super Mario Odyssey
No adaptive opponents whatsoever.
Millipede leans clearly harder on variance.
Millipede
Spawn waves and DDT timing vary run to run
Super Mario Odyssey
Almost no randomness in level design.
Super Mario Odyssey leans clearly harder on optimization.
Millipede
Mushroom-field management is a thin strategic layer
Super Mario Odyssey
Moon routes and movement tech learnable.
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.