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 · Competitive PvP
Sony's mascot brawler where only Super attacks score kills, making meter management the whole game.

Execution · Competitive PvP
Territory control through shooter execution and constant prediction of adapting human teams.
PlayStation All-Stars Battle Royale leans Execution (Competitive PvP); Splatoon leans Execution (Competitive PvP).
Splatoon leans a little harder on execution, though the gap is small.
PlayStation All-Stars Battle Royale
Combo routes into Super meter need decent but modest hands.
Splatoon
Aim, swim-form movement and ink management are constant demands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
PlayStation All-Stars Battle Royale
Super-only kills make baiting human opponents the core decision.
Splatoon
Human opponents adapt flanks and pushes every match
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
PlayStation All-Stars Battle Royale
Items and four-player chaos add mild randomness.
Splatoon
Hidden squids in ink create momentary information gaps
Splatoon leans a little harder on optimization, though the gap is small.
PlayStation All-Stars Battle Royale
Meter-build efficiency per character is the solvable layer.
Splatoon
Weapon kits, map control timing and gear builds reward study
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.