head to head
Neither is simply harder - they are hard in different places. Sea of Thieves demands more variance; Super Smash Bros. Melee demands more execution.

Reads · Competitive PvP
Open-world pirate game with PvPvE ship combat.

Execution · Competitive PvP
A platform fighter with one of the highest execution ceilings in any competitive game, layered on top of deep human reads.
Sea of Thieves leans Reads (Competitive PvP); Super Smash Bros. Melee leans Execution (Competitive PvP).
Super Smash Bros. Melee leans clearly harder on execution.
Sea of Thieves
Ship sailing and naval gunnery require hands
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Super Smash Bros. Melee leans clearly harder on reads.
Sea of Thieves
PvP ship fights are pure mind games
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
Sea of Thieves leans clearly harder on variance.
Sea of Thieves
Server encounters, weather, loot vary
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Super Smash Bros. Melee leans a little harder on optimization, though the gap is small.
Sea of Thieves
Routes, loadouts, ship setups solvable
Super Smash Bros. Melee
Character matchup tiers and optimal movement routing are deeply studied
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.