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

Optimization · Systems & Chaos
Notorious FMV horror adventure of a writer unraveling her mansion's grisly past.

Optimization · Systems & Chaos
A wordless surreal exploration game about wandering a sleeping girl's dreamscapes.
Phantasmagoria leans Optimization (Systems & Chaos); Yume Nikki leans Optimization (Systems & Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Phantasmagoria
Point-and-click with rare timed scenes
Yume Nikki
Just walking, no challenge on inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Phantasmagoria
Horror beats are fully scripted
Yume Nikki
No opponent of any kind
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Phantasmagoria
Deaths and triggers unknown on first run
Yume Nikki
Random events and obscure unknown triggers
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Phantasmagoria
Linear puzzle chains with single solutions
Yume Nikki
Mapping the dream worlds to find 24 effects
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.