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

Execution · Competitive PvP
Couch-competitive dexterity duels where reading the friend beside you wins games.

Execution · Competitive PvP
Wrestling crude controls to land specials while outguessing a human opponent.
Sportsfriends leans Execution (Competitive PvP); Street Fighter 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.
Sportsfriends
Pole vaults, joust balance and ball control demand real dexterity
Street Fighter
Notoriously stiff inputs make landing specials the real fight
Sportsfriends leans a little harder on reads, though the gap is small.
Sportsfriends
Couch opponents bait and adapt face-to-face every round
Street Fighter
Human versus rounds still reward bait and punish
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Sportsfriends
Arenas are fixed, nothing hidden
Street Fighter
Nothing hidden between two visible fighters
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Sportsfriends
Minimal systems - the games are deliberately simple rulesets
Street Fighter
Tiny moveset leaves little system to solve
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.