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.

Optimization · Pure Optimization
Solvable team-building progression through Sinnoh's fixed trainers.

Optimization · Pure Optimization
A farm-life sim solved by season routing and profit optimization.
Pokémon Diamond Version leans Optimization (Pure Optimization); Stardew Valley leans Optimization (Pure Optimization).
Stardew Valley leans a little harder on execution, though the gap is small.
Pokémon Diamond Version
Menu battles need no dexterity
Stardew Valley
Trivial timing on fishing and combat
Pokémon Diamond Version leans a little harder on reads, though the gap is small.
Pokémon Diamond Version
Scripted trainers never adapt; online battles are optional
Stardew Valley
No adaptive opponent exists
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Pokémon Diamond Version
Encounter and crit rolls are bounded, mappable randomness
Stardew Valley
Crop luck and geode RNG matter modestly
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Pokémon Diamond Version
Physical-special split deepens solvable team building
Stardew Valley
Routing seasons, profit loops, and bundles dominates
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.