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 · Practiced Mastery
Fan-built ground-up remake of Half-Life with a reimagined Xen.

Execution · Practiced Mastery
Dash-precision platforming with solvable boss orders and upgrade routing.
Black Mesa leans Execution (Practiced Mastery); Mega Man X5 leans Execution (Practiced Mastery).
Mega Man X5 leans a little harder on execution, though the gap is small.
Black Mesa
Classic FPS aim and platforming sequences
Mega Man X5
Dash-jump precision and boss dodge timing demand clean hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Black Mesa
Marines and aliens follow set scripts
Mega Man X5
Mavericks cycle fixed attack patterns
Black Mesa leans a little harder on variance, though the gap is small.
Black Mesa
Minor enemy placement surprises first run
Mega Man X5
Random ending triggers add rare unmapped outcomes
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Black Mesa
Route, resource, and encounter knowledge
Mega Man X5
Armor parts, boss order and route knowledge solve the game
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.