head to head
Neither is simply harder - they are hard in different places. SCP: Secret Laboratory demands more variance; Super Smash Bros. Melee demands more execution.

Execution · Competitive PvP
Chaotic asymmetric rounds testing aim, facility knowledge and reading untrustworthy humans.

Execution · Competitive PvP
A platform fighter with one of the highest execution ceilings in any competitive game, layered on top of deep human reads.
SCP: Secret Laboratory leans Execution (Competitive PvP); Super Smash Bros. Melee leans Execution (Competitive PvP).
Super Smash Bros. Melee leans clearly harder on execution.
SCP: Secret Laboratory
Gunfights and SCP chases demand aim and movement
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Super Smash Bros. Melee leans clearly harder on reads.
SCP: Secret Laboratory
Human teams bluff, betray and negotiate constantly
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
SCP: Secret Laboratory leans clearly harder on variance.
SCP: Secret Laboratory
Random spawns, items and facility layout each round
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Super Smash Bros. Melee leans clearly harder on optimization.
SCP: Secret Laboratory
Class knowledge, keycard routes and zone control reward mastery
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.