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 · Practiced Mastery
The fastest mainline Souls, distilling the formula into aggressive boss duels.

Execution · Practiced Mastery
A stance-action RPG carried by ki-pulse timing and loot build optimization.
Dark Souls III leans Execution (Practiced Mastery); Nioh leans Execution (Practiced Mastery).
Nioh leans a little harder on execution, though the gap is small.
Dark Souls III
fast roll timing against aggressive scripted bosses
Nioh
Stance and ki-pulse timing demand inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
PvP invasions exist but are optional
Nioh
Scripted enemies
Nioh leans a little harder on variance, though the gap is small.
Dark Souls III
fixed encounters converge after first sight
Nioh
Loot affix rolls
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
movesets and builds are fully mappable
Nioh
Build crafting and stance routing reward planning
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.