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
Twitch dodging and shooting layered over memorised arcade stage routes.

Execution · Pure Mechanics
Twitch dodging and aim under fire, with score routes rewarding memorisation.
Metal Slug leans Execution (Practiced Mastery); Sin & Punishment: Star Successor leans Execution (Pure Mechanics).
Sin & Punishment: Star Successor leans a little harder on execution, though the gap is small.
Metal Slug
Dodging dense bullet patterns and precise shots carry every credit
Sin & Punishment: Star Successor
Dodging dense bullet patterns while aiming is a motor ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug
Enemies follow fixed arcade scripts, never adapt
Sin & Punishment: Star Successor
Bosses follow elaborate but fixed scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug
Spawns are nearly deterministic once a stage is learned
Sin & Punishment: Star Successor
Everything is deterministic once patterns are seen
Metal Slug leans a little harder on optimization, though the gap is small.
Metal Slug
One-credit clears come from memorising routes and spawn patterns
Sin & Punishment: Star Successor
Multiplier preservation routes drive leaderboard play
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.