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
KOF's jump to 3D visuals with a huge fifty-character launch roster.

Execution · Grand Arena
A hyper-fast tag fighting game defined by three-character teams and touch-of-death combos.
The King of Fighters XIV leans Execution (Competitive PvP); Ultimate Marvel vs. Capcom 3 leans Execution (Grand Arena).
Ultimate Marvel vs. Capcom 3 leans a little harder on execution, though the gap is small.
The King of Fighters XIV
Max mode confirms and hop pressure test hands
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.
The King of Fighters XIV
Classic KOF human mixups demand continual reading
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.
The King of Fighters XIV
Deterministic 3v3 combat
Ultimate Marvel vs. Capcom 3
Almost fully deterministic
Ultimate Marvel vs. Capcom 3 leans a little harder on optimization, though the gap is small.
The King of Fighters XIV
Team order and max-mode damage routes are studied
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.