head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, 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
Classic fighting game testing execution precision and human mix-up prediction.
Marvel vs. Capcom: Clash of Super Heroes leans Execution (Competitive PvP); Street Fighter Alpha: Warriors' Dreams leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom: Clash of Super Heroes
Chain combos, assists and infinites demand fast precise hands
Street Fighter Alpha: Warriors' Dreams
Motion inputs, links and Alpha Counters demand clean 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
Street Fighter Alpha: Warriors' Dreams
Footsies and throw mix-ups against a human are the heart
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
Street Fighter Alpha: Warriors' Dreams
Full information once the round starts
Marvel vs. Capcom: Clash of Super Heroes leans a little harder on optimization, though the gap is small.
Marvel vs. Capcom: Clash of Super Heroes
Team composition and infinite-combo knowledge define the meta
Street Fighter Alpha: Warriors' Dreams
Matchup knowledge and meter management are studyable theory
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.
full breakdown
Marvel vs. Capcom: Clash of Super Heroes →
full breakdown
Street Fighter Alpha: Warriors' Dreams →