head to head
Neither is simply harder - they are hard in different places. Super Smash Bros. Melee demands more execution; Worms W.M.D demands more variance.

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

Reads · Competitive PvP
Modern Worms with crafting and vehicles, keeping the classic turn-based destructible-terrain warfare.
Super Smash Bros. Melee leans Execution (Competitive PvP); Worms W.M.D leans Reads (Competitive PvP).
Super Smash Bros. Melee leans clearly harder on execution.
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Worms W.M.D
Shot arcs, rope swings and vehicle control demand precision
Super Smash Bros. Melee leans clearly harder on reads.
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
Worms W.M.D
Multiplayer turns hinge on out-guessing rival worm placement
Worms W.M.D leans clearly harder on variance.
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Worms W.M.D
Wind, crates and random terrain reshape options
Super Smash Bros. Melee leans a little harder on optimization, though the gap is small.
Super Smash Bros. Melee
Character matchup tiers and optimal movement routing are deeply studied
Worms W.M.D
Crafting and weapon budgeting reward planned turns
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.