head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
Hardest modern-era Fire Emblem, a sprawling multi-army tactics campaign where planning around hit RNG is everything.

Optimization · Pure Optimization
An auto-attacker where picking the right weapon evolutions wins by itself.
Fire Emblem: Radiant Dawn 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: Radiant Dawn
Grid menus; no physical skill.
Vampire Survivors
Movement is trivial; no aim or precision required.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fire Emblem: Radiant Dawn
Enemy AI follows exploitable fixed priorities.
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: Radiant Dawn
Hit, crit, and level-up rolls threaten permadeath plans.
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: Radiant Dawn
Unit deployment, BEXP routing, and map solutions dominate.
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.