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

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

Optimization · Systems & Chaos
Managing hidden stats day by day to steer toward chosen endings.
Fallout Shelter leans Optimization (Pure Optimization); Needy Streamer Overload 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.
Fallout Shelter
Tapping menus only
Needy Streamer Overload
Desktop clicks only
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
Needy Streamer Overload
Ame's reactions are scripted stat thresholds, not an adapting mind
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout Shelter
Incident spawns and lunchbox loot rolls
Needy Streamer Overload
Hidden stat thresholds and event rolls obscure ending routes
Fallout Shelter leans a little harder on optimization, though the gap is small.
Fallout Shelter
Dweller stats and room layout are fully solvable
Needy Streamer Overload
Mapping the stat system to reach target endings is the game
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.