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

Execution · Competitive PvP
The classic 'dream match' team fighter widely held as KOF's most balanced competitive entry.
Street Fighter X Tekken leans Execution (Grand Arena); The King of Fighters '98 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
The King of Fighters '98
Strict inputs, short hops, tight punishes
The King of Fighters '98 leans a little harder on reads, though the gap is small.
Street Fighter X Tekken
Human mixups and tag baits require adaptation
The King of Fighters '98
Human opponents constantly adapt and condition you
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Street Fighter X Tekken
Deterministic aside from negligible elements
The King of Fighters '98
Near-fully visible game state
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
The King of Fighters '98
Team order and matchup theory reward study
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.