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

Execution · Grand Arena
A variation-based fighter where character specialisation choices and read-and-punish execution drive competitive outcomes.

Execution · Competitive PvP
Out-executing and out-predicting another human in frame-precise duels.
Mortal Kombat X leans Execution (Grand Arena); Super Street Fighter IV: 3D Edition 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 X
Variation-specific combo routes demand precise practice
Super Street Fighter IV: 3D Edition
Links, anti-airs and motion inputs gate every level of play
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat X
Reading opponent's variation choice and tendency shifts the matchup
Super Street Fighter IV: 3D Edition
Footsies and conditioning a human opponent decide matches
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat X
No RNG; transparent match flow
Super Street Fighter IV: 3D Edition
Almost fully deterministic once inputs land
Mortal Kombat X leans a little harder on optimization, though the gap is small.
Mortal Kombat X
Variation selection and optimal punish routes require systematic study
Super Street Fighter IV: 3D Edition
Frame data, matchup knowledge and punish routes underpin everything
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.