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

Variance · Systems & Chaos
Turn-based resource management through randomly generated dungeon layouts.

Variance · Systems & Chaos
A gothic narrative exploration game about flying a steam locomotive through haunted skies.
Pokémon Mystery Dungeon: Red Rescue Team leans Variance (Systems & Chaos); Sunless Skies leans Variance (Systems & Chaos).
Sunless Skies leans a little harder on execution, though the gap is small.
Pokémon Mystery Dungeon: Red Rescue Team
Turn-based grid movement - no twitch demands
Sunless Skies
Slow locomotive combat asks little of the hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Pokémon Mystery Dungeon: Red Rescue Team
Wild Pokémon follow simple deterministic AI
Sunless Skies
Horrors and agents follow scripted storylets
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Pokémon Mystery Dungeon: Red Rescue Team
Random dungeon layouts, items and encounters each run
Sunless Skies
Hidden ports, story branches and terror events
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Pokémon Mystery Dungeon: Red Rescue Team
Team building, item management and type matchups carry runs
Sunless Skies
Trade routes and fuel economics are plannable
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.