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
High-speed tag-team execution and human prediction in gleeful early-Versus chaos.

Execution · Competitive PvP
The Dreamcast classic that defined weapons-based 3D fighting with fluid eight-way movement.
Marvel vs. Capcom: Clash of Super Heroes leans Execution (Competitive PvP); Soulcalibur leans Execution (Competitive PvP).
Marvel vs. Capcom: Clash of Super Heroes leans a little harder on execution, though the gap is small.
Marvel vs. Capcom: Clash of Super Heroes
Chain combos, assists and infinites demand fast precise hands
Soulcalibur
Eight-way run and precise spacing reward sharp movement hands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom: Clash of Super Heroes
Baiting a human's assist call or super is the duel
Soulcalibur
Mid-low-throw mixups and Guard Impact baits against adapting opponents.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom: Clash of Super Heroes
Hidden characters aside, everything is public
Soulcalibur
Fully deterministic; no hidden systems.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom: Clash of Super Heroes
Team composition and infinite-combo knowledge define the meta
Soulcalibur
Ring-out positioning and frame knowledge 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.