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
Arcade western shooter narrated as a bounty hunter's tall tale.

Execution · Practiced Mastery
Twitch dodging and shooting layered over memorised arcade stage routes.
Call of Juarez: Gunslinger leans Execution (Practiced Mastery); Metal Slug leans Execution (Practiced Mastery).
Metal Slug leans a little harder on execution, though the gap is small.
Call of Juarez: Gunslinger
Quick-draw duels and combo shooting demand precision
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.
Call of Juarez: Gunslinger
Enemies are scripted gallery targets
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.
Call of Juarez: Gunslinger
Minor enemy placement surprises first run
Metal Slug
Spawns are nearly deterministic once a stage is learned
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Juarez: Gunslinger
Score routes, skill trees, duel timing knowledge
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.