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
A run-and-gun arcade shooter that is almost pure twitch execution.

Execution · Pure Mechanics
A brutally precise platformer about dying thousands of times.
Metal Slug 5 leans Execution (Pure Mechanics); Super Meat Boy leans Execution (Pure Mechanics).
Super Meat Boy leans a little harder on execution, though the gap is small.
Metal Slug 5
precise dodge/shoot run-and-gun demands
Super Meat Boy
Pure twitch platforming, frame-perfect jumps
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug 5
enemy waves are fully scripted patterns
Super Meat Boy
No adaptive opponent
Metal Slug 5 leans a little harder on variance, though the gap is small.
Metal Slug 5
minor drop and spawn randomness
Super Meat Boy
Fully deterministic levels
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug 5
weapon pickup and route memorization
Super Meat Boy
Route memorization optimizes times
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.