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 · Competitive PvP
The definitive classic Street Fighter II revision and a founding tournament fighter.

Execution · Competitive PvP
The classic 'dream match' team fighter widely held as KOF's most balanced competitive entry.
Super Street Fighter II Turbo leans Execution (Competitive PvP); The King of Fighters '98 leans Execution (Competitive PvP).
Super Street Fighter II Turbo leans a little harder on execution, though the gap is small.
Super Street Fighter II Turbo
One-frame links, charge timing, and strict motions
The King of Fighters '98
Strict inputs, short hops, tight punishes
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Super Street Fighter II Turbo
Footsies and throw mixups against an adapting human
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.
Super Street Fighter II Turbo
Minor damage variation; everything else visible
The King of Fighters '98
Near-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.
Super Street Fighter II Turbo
Matchup knowledge and super meter spend are studied lines
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.