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
Wrangling high-speed 3D movement through fixed stages and boss scripts.

Execution · Practiced Mastery
Mid-demand 3D platforming execution across fixed gravity puzzles.
Sonic Adventure DX: Director's Cut 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.
Sonic Adventure DX: Director's Cut
High-speed 3D control and jank-wrangling demand real hands
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.
Sonic Adventure DX: Director's Cut
Chaos bosses run fixed phase scripts
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.
Sonic Adventure DX: Director's Cut
Stage layouts and upgrades never change
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.
Sonic Adventure DX: Director's Cut
Speedrun routing and A-rank paths are learnable systems
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.