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
The toned-down crossover fighter matching Mortal Kombat's roster against DC superheroes.

Execution · Competitive PvP
Tests arena brawling timing and skill-build crafting against human opponents.
Mortal Kombat vs. DC Universe leans Execution (Competitive PvP); Sonic Battle leans Execution (Competitive PvP).
Mortal Kombat vs. DC Universe leans a little harder on execution, though the gap is small.
Mortal Kombat vs. DC Universe
Juggle combos and klose kombat timing
Sonic Battle
Aerial juggles and guard timing on a grid arena
Mortal Kombat vs. DC Universe leans a little harder on reads, though the gap is small.
Mortal Kombat vs. DC Universe
Human mixups, though a simpler toolset than peers
Sonic Battle
Versus humans, baiting special skill choices is the edge
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat vs. DC Universe
Deterministic crossover combat
Sonic Battle
Little randomness beyond skill-card drops
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat vs. DC Universe
Mapping juggle routes and matchup tools rewards practice
Sonic Battle
Custom skill builds for Emerl define the meta
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.