head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Competitive PvP
Lab-honed combo execution plus live mixup guessing against adapting human opponents.

Execution · Grand Arena
A hyper-fast tag fighting game defined by three-character teams and touch-of-death combos.
Skullgirls: 2nd Encore 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.
Skullgirls: 2nd Encore
Long combo routes and tight conversions demand serious hands
Ultimate Marvel vs. Capcom 3
Long touch-of-death combos demand elite hands
Ultimate Marvel vs. Capcom 3 leans a little harder on reads, though the gap is small.
Skullgirls: 2nd Encore
Mixups and resets only work by out-guessing a 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.
Skullgirls: 2nd Encore
Fully deterministic fighter with nothing hidden
Ultimate Marvel vs. Capcom 3
Almost fully deterministic
Ultimate Marvel vs. Capcom 3 leans a little harder on optimization, though the gap is small.
Skullgirls: 2nd Encore
Team composition, assists and combo theory go deep
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.