head to head
Ketsui: Kizuna Jigoku Tachi asks more than Metal Slug, and the gap is execution.

Execution · Pure Mechanics
Cave's hardest bullet hell, built on suicidal close-range scoring and merciless execution demands.

Execution · Practiced Mastery
Twitch dodging and shooting layered over memorised arcade stage routes.
Ketsui: Kizuna Jigoku Tachi leans Execution (Pure Mechanics); Metal Slug leans Execution (Practiced Mastery).
Ketsui: Kizuna Jigoku Tachi leans clearly harder on execution.
Ketsui: Kizuna Jigoku Tachi
Point-blank chip harvesting in bullet storms, brutal physical ceiling
Metal Slug
Dodging dense bullet patterns and precise shots carry every credit
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Ketsui: Kizuna Jigoku Tachi
Enemies follow fixed scripts
Metal Slug
Enemies follow fixed arcade scripts, never adapt
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Ketsui: Kizuna Jigoku Tachi
Deterministic patterns, trivial randomness
Metal Slug
Spawns are nearly deterministic once a stage is learned
Ketsui: Kizuna Jigoku Tachi leans a little harder on optimization, though the gap is small.
Ketsui: Kizuna Jigoku Tachi
Multiplier chip routing is a solved-route discipline
Metal Slug
One-credit clears come from memorising routes and spawn patterns
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.