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
A vault management sim about optimising dwellers, rooms, and resource loops.

Optimization · Systems & Chaos
A gentle remake of the original Pokémon Mystery Dungeon rescue adventures with modern conveniences.
Fallout Shelter leans Optimization (Pure Optimization); Pokémon Mystery Dungeon: Rescue Team DX leans Optimization (Systems & Chaos).
Pokémon Mystery Dungeon: Rescue Team DX leans a little harder on execution, though the gap is small.
Fallout Shelter
Tapping menus only
Pokémon Mystery Dungeon: Rescue Team DX
Turn-based with auto-modes; no dexterity
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout Shelter
No opponent
Pokémon Mystery Dungeon: Rescue Team DX
No adaptive opponent
Pokémon Mystery Dungeon: Rescue Team DX leans a little harder on variance, though the gap is small.
Fallout Shelter
Incident spawns and lunchbox loot rolls
Pokémon Mystery Dungeon: Rescue Team DX
Random dungeons softened by generous remake systems
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout Shelter
Dweller stats and room layout are fully solvable
Pokémon Mystery Dungeon: Rescue Team DX
Team building and rare qualities reward 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.