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
Supercell's snappy top-down team brawler built around three-minute objective fights.

Execution · Competitive PvP
Territory control through shooter execution and constant prediction of adapting human teams.
Brawl Stars leans Execution (Competitive PvP); Splatoon leans Execution (Competitive PvP).
Splatoon leans a little harder on execution, though the gap is small.
Brawl Stars
Aim, dodging, and ability timing in real time
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.
Brawl Stars
Human teams rotate, bait supers, and adapt
Splatoon
Human opponents adapt flanks and pushes every match
Brawl Stars leans a little harder on variance, though the gap is small.
Brawl Stars
Bush ambushes and power-cube spawns hide information
Splatoon
Hidden squids in ink create momentary information gaps
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Brawl Stars
Brawler matchups and map strategy are learnable
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.