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 · Grand Arena
Chaotic tag fighter whose top tiers reward blistering execution and assist mastery.

Execution · Competitive PvP
The definitive classic Street Fighter II revision and a founding tournament fighter.
Marvel vs. Capcom 2: New Age of Heroes leans Execution (Grand Arena); Super Street Fighter II Turbo 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 2: New Age of Heroes
infinite combos and assist timing demand elite hands
Super Street Fighter II Turbo
One-frame links, charge timing, and strict motions
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom 2: New Age of Heroes
humans bait assists and mix high-low constantly
Super Street Fighter II Turbo
Footsies and throw mixups against an adapting human
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Marvel vs. Capcom 2: New Age of Heroes
fully deterministic engine
Super Street Fighter II Turbo
Minor damage variation; everything else visible
Marvel vs. Capcom 2: New Age of Heroes leans a little harder on optimization, though the gap is small.
Marvel vs. Capcom 2: New Age of Heroes
team order, assist synergy, and matchup knowledge
Super Street Fighter II Turbo
Matchup knowledge and super meter spend are studied lines
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.