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
Pioneering six-degrees-of-freedom shooter through robot-infested mines.

Execution · Practiced Mastery
Punishing platforming execution over learnable boss orders and part builds.
Descent leans Execution (Practiced Mastery); Mega Man X6 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.
Descent
Full 6DOF control and aim under disorientation is the test
Mega Man X6
Cruel platforming and boss windows demand frame-tight inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Descent
Scripted robot behaviors, no adaptation
Mega Man X6
Bosses are fixed pattern sets
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Descent
Mine layouts fixed; ambushes surprise only once
Mega Man X6
The Nightmare System shuffles level hazards between runs
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Descent
Route memorization and weapon economy reward optimization
Mega Man X6
Weapon orders, armor parts and route knowledge are essential
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.