head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, 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
Tests trajectory aim and turn planning against human targets amid crate luck.
Brawl Stars leans Execution (Competitive PvP); Worms: Ultimate Mayhem leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Brawl Stars
Aim, dodging, and ability timing in real time
Worms: Ultimate Mayhem
3D grenade arcs and ninja-rope control reward practiced aim
Brawl Stars leans a little harder on reads, though the gap is small.
Brawl Stars
Human teams rotate, bait supers, and adapt
Worms: Ultimate Mayhem
Predicting a human's target priorities shapes each turn
Worms: Ultimate Mayhem leans a little harder on variance, though the gap is small.
Brawl Stars
Bush ambushes and power-cube spawns hide information
Worms: Ultimate Mayhem
Crate drops, wind and terrain chaos swing rounds
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
Worms: Ultimate Mayhem
Weapon economy and positioning are plannable each turn
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.