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.

Reads · Competitive PvP
The Wii entry whose slower pace and infamous random tripping pushed Smash toward defensive mind games.
Brawl Stars leans Execution (Competitive PvP); Super Smash Bros. Brawl leans Reads (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
Super Smash Bros. Brawl
Slower engine lowers the ceiling but spacing still needs hands.
Super Smash Bros. Brawl leans a little harder on reads, though the gap is small.
Brawl Stars
Human teams rotate, bait supers, and adapt
Super Smash Bros. Brawl
Defensive bait-and-punish yomi dominates its floaty neutral.
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
Super Smash Bros. Brawl
Random tripping injects genuine uncontrollable RNG into movement.
Brawl Stars leans a little harder on optimization, though the gap is small.
Brawl Stars
Brawler matchups and map strategy are learnable
Super Smash Bros. Brawl
Matchup knowledge and ledge play reward study within a campy meta.
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.