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.

Optimization · Pure Optimization
A tactical RPG where careful positioning and managing randomized combat odds decides survival.

Optimization · Pure Optimization
An auto-attacker where picking the right weapon evolutions wins by itself.
Fire Emblem leans Optimization (Pure Optimization); Vampire Survivors leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Fire Emblem
no real-time physical skill, turn-based
Vampire Survivors
Movement is trivial; no aim or precision required.
Fire Emblem leans a little harder on reads, though the gap is small.
Fire Emblem
AI is scripted, no true adaptation
Vampire Survivors
Enemies follow fixed spawn scripts; no adaptive opponent.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fire Emblem
hit chance rolls are heavily randomized
Vampire Survivors
Level-up offerings and pickup drops are randomized.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fire Emblem
permadeath tactics and builds near-solvable
Vampire Survivors
Evolution paths and weapon combinations fully solve the run.
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.