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

Execution · Grand Arena
A tag-team crossover fighter pitting Street Fighter's cast against Tekken's under Capcom rules.

Execution · Competitive PvP
A platform fighter where reading opponents and precise execution both drive victory.
Street Fighter X Tekken leans Execution (Grand Arena); Super Smash Bros. for Nintendo 3DS 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.
Street Fighter X Tekken
Tag combos and juggle timing demand practiced hands
Super Smash Bros. for Nintendo 3DS
precise inputs and combo execution required
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Street Fighter X Tekken
Human mixups and tag baits require adaptation
Super Smash Bros. for Nintendo 3DS
reading opponent habits and mixups
Super Smash Bros. for Nintendo 3DS leans a little harder on variance, though the gap is small.
Street Fighter X Tekken
Deterministic aside from negligible elements
Super Smash Bros. for Nintendo 3DS
item spawns add randomness
Street Fighter X Tekken leans a little harder on optimization, though the gap is small.
Street Fighter X Tekken
Gem loadouts and team synergy add a builder layer
Super Smash Bros. for Nintendo 3DS
matchup knowledge and combos solvable
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.