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
A combo-heavy 3D fighter where lab-trained hands meet live human prediction.
Marvel vs. Capcom: Clash of Super Heroes leans Execution (Competitive PvP); Tekken 6 leans Execution (Competitive PvP).
Tekken 6 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
Tekken 6
Bound combos and movement push a high physical ceiling
Tekken 6 leans a little harder on reads, though the gap is small.
Marvel vs. Capcom: Clash of Super Heroes
Baiting a human's assist call or super is the duel
Tekken 6
Rage comebacks amplify the human guessing game
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
Tekken 6
Visible state; nothing meaningfully random
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
Tekken 6
Optimal bound routes and punishment charts are lab work
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.