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

Execution · Pure Mechanics
A boss-rush action game that is nothing but execution tests against scripted duelists.

Execution · Pure Mechanics
Punishing combat execution against fast scripted enemies with deep encounter solutions.
Furi leans Execution (Pure Mechanics); Ninja Gaiden II Black leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Furi
Parry timing, bullet dodging, and duel precision
Ninja Gaiden II Black
Frame-tight blocking, dodging and combo routing define survival
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Furi
Bosses are scripted patterns, however adversarial they feel
Ninja Gaiden II Black
Aggressive enemies still run scripted, learnable behaviour
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Furi
Fixed boss sequences
Ninja Gaiden II Black
Encounters fixed; spawns known after one run
Ninja Gaiden II Black leans a little harder on optimization, though the gap is small.
Furi
Learning each boss's phases converges to mastery
Ninja Gaiden II Black
Weapon choice, essence economy and encounter solutions matter
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.