head to head
Neither is simply harder - they are hard in different places. Endzone - A World Apart demands more variance; Fallout: New Vegas demands more execution.

Optimization · Pure Optimization
Post-apocalyptic city builder about balancing water, radiation, and morale against random disasters.

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.
Endzone - A World Apart leans Optimization (Pure Optimization); Fallout: New Vegas leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Endzone - A World Apart
Pause-friendly mouse-driven management
Fallout: New Vegas
Shooter inputs with VATS assist
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Endzone - A World Apart
No adaptive opposition
Fallout: New Vegas
Scripted factions and enemies
Endzone - A World Apart leans clearly harder on variance.
Endzone - A World Apart
Droughts, radiation, and raider events arrive semi-randomly
Fallout: New Vegas
Some loot and crit RNG
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Endzone - A World Apart
Resource chains and settlement layout are the whole game
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
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.