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 · Grand Arena
Team hero shooter blending FPS mechanics with ability economy mind games.

Execution · Grand Arena
Frantic tag-team fighter crossing Capcom's mutants with World Warriors.
Overwatch leans Execution (Grand Arena); X-Men vs. Street Fighter leans Execution (Grand Arena).
X-Men vs. Street Fighter leans a little harder on execution, though the gap is small.
Overwatch
Hero aim, movement, and ability timing
X-Men vs. Street Fighter
Infinite combos and tag execution demand serious hands.
X-Men vs. Street Fighter leans a little harder on reads, though the gap is small.
Overwatch
Ult tracking, flanks, and baiting human teams
X-Men vs. Street Fighter
Human opponents adapt mixups every round.
Overwatch leans a little harder on variance, though the gap is small.
Overwatch
Minor spread and matchmaking noise
X-Men vs. Street Fighter
Fully visible game state.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Overwatch
Team comps, ult economy, and positioning theory
X-Men vs. Street Fighter
Team synergy and matchup theory reward lab time.
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.