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
Mapping dungeons and engineering party builds against chartable threats.

Optimization · Pure Optimization
Small-town murder-mystery JRPG balancing friendships by day and TV-world dungeons by night.
Etrian Odyssey Untold: The Millennium Girl leans Optimization (Pure Optimization); Persona 4 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.
Etrian Odyssey Untold: The Millennium Girl
Turn-based menus require no dexterity
Persona 4
Menu combat; zero dexterity
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Etrian Odyssey Untold: The Millennium Girl
FOE patterns are scripted and chartable
Persona 4
Shadow bosses use scripted patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Etrian Odyssey Untold: The Millennium Girl
Unknown floors and ambushes punish until mapped
Persona 4
Randomized dungeon floors and fusion rolls
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Etrian Odyssey Untold: The Millennium Girl
Party builds, skill synergies and map routing dominate
Persona 4
Social link scheduling and weakness-exploit 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.