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

Execution · Practiced Mastery
Arcade dogfighting reflexes against scripted enemy flight patterns.

Execution · Practiced Mastery
Mid-demand 3D platforming execution across fixed gravity puzzles.
Air Combat leans Execution (Practiced Mastery); Super Mario Galaxy leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Air Combat
Stick control and missile timing carry every dogfight
Super Mario Galaxy
Gravity-bending jumps need timing, though forgiving by Mario standards
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Air Combat
Enemy pilots fly scripted arcade patterns
Super Mario Galaxy
Bosses repeat fixed patterns - nothing adapts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Air Combat
Missions are fixed and fully learnable
Super Mario Galaxy
Galaxies are scripted; surprises evaporate after one visit
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Air Combat
Plane purchases and mission knowledge smooth the campaign
Super Mario Galaxy
Star routes and comet challenges reward learned solutions
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.