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
The second Versus-series crossover, escalating tag-team chaos with assists and screen-filling supers.

Execution · Competitive PvP
The Wii U Smash that restored competitive pace and a huge roster of labbable kill confirms.
Marvel Super Heroes vs. Street Fighter leans Execution (Competitive PvP); Super Smash Bros. for Wii U leans Execution (Competitive PvP).
Marvel Super Heroes vs. Street Fighter leans a little harder on execution, though the gap is small.
Marvel Super Heroes vs. Street Fighter
Long air chains, assists, and infinites set a high physical bar.
Super Smash Bros. for Wii U
Perfect pivots and precise aerial spacing reward sharp hands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel Super Heroes vs. Street Fighter
Tag and assist mixups against adapting humans drive wins.
Super Smash Bros. for Wii U
Ledge-trap and landing-trap guessing against humans never converges.
Super Smash Bros. for Wii U leans a little harder on variance, though the gap is small.
Marvel Super Heroes vs. Street Fighter
Deterministic chaos; everything visible.
Super Smash Bros. for Wii U
Tripping removed; only minor move RNG remains.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel Super Heroes vs. Street Fighter
Team synergy and touch-of-death routes are deeply solvable.
Super Smash Bros. for Wii U
Rage mechanics and kill-confirm percents are deeply labbable.
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.