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

Optimization · Pure Optimization
A dialogue RPG resolved by stat builds against dice checks.

Optimization · Pure Optimization
A vault management sim about optimising dwellers, rooms, and resource loops.
Disco Elysium leans Optimization (Pure Optimization); Fallout Shelter 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.
Disco Elysium
No mechanical inputs of consequence
Fallout Shelter
Tapping menus only
Disco Elysium leans a little harder on reads, though the gap is small.
Disco Elysium
Dialogue partners are scripted, not modeling you
Fallout Shelter
No opponent
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Disco Elysium
Skill checks roll dice with hidden modifiers
Fallout Shelter
Incident spawns and lunchbox loot rolls
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Disco Elysium
Build skills and route choices to pass checks
Fallout Shelter
Dweller stats and room layout are fully solvable
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.