head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Competitive PvP
A platform fighter with one of the highest execution ceilings in any competitive game, layered on top of deep human reads.

Execution · Grand Arena
A hyper-fast tag fighting game defined by three-character teams and touch-of-death combos.
Super Smash Bros. Melee leans Execution (Competitive PvP); Ultimate Marvel vs. Capcom 3 leans Execution (Grand Arena).
Super Smash Bros. Melee leans a little harder on execution, though the gap is small.
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Ultimate Marvel vs. Capcom 3
Long touch-of-death combos demand elite hands
Super Smash Bros. Melee leans a little harder on reads, though the gap is small.
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
Ultimate Marvel vs. Capcom 3
Mixups and assist baits versus adapting humans
Super Smash Bros. Melee leans a little harder on variance, though the gap is small.
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Ultimate Marvel vs. Capcom 3
Almost fully deterministic
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Super Smash Bros. Melee
Character matchup tiers and optimal movement routing are deeply studied
Ultimate Marvel vs. Capcom 3
Team composition and matchup knowledge run deep
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.