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
Arcade reflexes against memorisable alien swarm patterns built to eat quarters.

Execution · Pure Mechanics
A 3D platformer whose joy lives in tight movement and capture-driven traversal.
Aliens leans Execution (Pure Mechanics); Super Mario Odyssey leans Execution (Pure Mechanics).
Super Mario Odyssey leans a little harder on execution, though the gap is small.
Aliens
Arcade dodging and shooting under swarm pressure is the test
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.
Aliens
Xenomorph waves follow scripted arcade patterns
Super Mario Odyssey
No adaptive opponents whatsoever.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Aliens
Stage layouts and spawns are fixed
Super Mario Odyssey
Almost no randomness in level design.
Super Mario Odyssey leans a little harder on optimization, though the gap is small.
Aliens
Learning spawn points and weapon pickups carries credit-saving runs
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.