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

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.

Optimization · Pure Optimization
A gothic horror RPG blending survival-horror atmosphere with tactical grid battles in a haunted Welsh monastery.
Fallout: New Vegas leans Optimization (Pure Optimization); Koudelka leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Fallout: New Vegas
Shooter inputs with VATS assist
Koudelka
Turn-based grid combat, no dexterity
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Fallout: New Vegas
Scripted factions and enemies
Koudelka
Monsters act on simple fixed logic
Koudelka leans clearly harder on variance.
Fallout: New Vegas
Some loot and crit RNG
Koudelka
Random encounters and drop rolls
Fallout: New Vegas leans a little harder on optimization, though the gap is small.
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
Koudelka
Stat allocation and durability planning decide fights
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.