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
A hero battle royale where teamwork and aim against human opponents decides fights.
Brawl Stars leans Execution (Competitive PvP); My Hero Ultra Rumble leans Execution (Competitive PvP).
My Hero Ultra Rumble leans a little harder on execution, though the gap is small.
Brawl Stars
Aim, dodging, and ability timing in real time
My Hero Ultra Rumble
aim and combo timing in battles
Brawl Stars leans a little harder on reads, though the gap is small.
Brawl Stars
Human teams rotate, bait supers, and adapt
My Hero Ultra Rumble
predicting human opponent tactics
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Brawl Stars
Bush ambushes and power-cube spawns hide information
My Hero Ultra Rumble
item and loot drops are random
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
My Hero Ultra Rumble
team comps and loadouts solvable
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.