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
The definitive classic Street Fighter II revision and a founding tournament fighter.

Execution · Grand Arena
A hyper-fast tag fighting game defined by three-character teams and touch-of-death combos.
Super Street Fighter II Turbo leans Execution (Competitive PvP); Ultimate Marvel vs. Capcom 3 leans Execution (Grand Arena).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Super Street Fighter II Turbo
One-frame links, charge timing, and strict motions
Ultimate Marvel vs. Capcom 3
Long touch-of-death combos demand elite hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Super Street Fighter II Turbo
Footsies and throw mixups against an adapting human
Ultimate Marvel vs. Capcom 3
Mixups and assist baits versus adapting humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Super Street Fighter II Turbo
Minor damage variation; everything else visible
Ultimate Marvel vs. Capcom 3
Almost fully deterministic
Ultimate Marvel vs. Capcom 3 leans a little harder on optimization, though the gap is small.
Super Street Fighter II Turbo
Matchup knowledge and super meter spend are studied lines
Ultimate Marvel vs. Capcom 3
Team composition and matchup knowledge run deep
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.