head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Competitive PvP
Fighting-game execution and opponent prediction across an enormous, loosely balanced roster.

Execution · Competitive PvP
The toned-down crossover fighter matching Mortal Kombat's roster against DC superheroes.
Mortal Kombat: Armageddon leans Execution (Competitive PvP); Mortal Kombat vs. DC Universe 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.
Mortal Kombat: Armageddon
Combo strings and kombat timing decide exchanges
Mortal Kombat vs. DC Universe
Juggle combos and klose kombat timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat: Armageddon
Versus humans, baiting and punishing habits is the meta
Mortal Kombat vs. DC Universe
Human mixups, though a simpler toolset than peers
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat: Armageddon
No hidden information once movesets are known
Mortal Kombat vs. DC Universe
Deterministic crossover combat
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat: Armageddon
A 62-character roster of matchup knowledge to internalise
Mortal Kombat vs. DC Universe
Mapping juggle routes and matchup tools rewards practice
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.