head to head
Super Smash Bros. Melee asks more than Day of Defeat: Source, and the gap is reads.

Execution · Competitive PvP
Team-based WWII infantry shooter about holding and capturing map points.

Execution · Competitive PvP
A platform fighter with one of the highest execution ceilings in any competitive game, layered on top of deep human reads.
Day of Defeat: Source leans Execution (Competitive PvP); Super Smash Bros. Melee leans Execution (Competitive PvP).
Super Smash Bros. Melee leans clearly harder on execution.
Day of Defeat: Source
Recoil control and snap aim decide most firefights
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Super Smash Bros. Melee leans clearly harder on reads.
Day of Defeat: Source
Human squads shift pushes and holds unpredictably
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Day of Defeat: Source
Known maps, minimal randomness beyond spawn waves
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Super Smash Bros. Melee leans clearly harder on optimization.
Day of Defeat: Source
Class loadouts and lane control are quickly mapped
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.