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

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

Optimization · Pure Optimization
A meta deckbuilder where engine-building beats the scripted opponent.
Fallout: New Vegas leans Optimization (Pure Optimization); Inscryption leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Fallout: New Vegas
Shooter inputs with VATS assist
Inscryption
No reflex demands; turn-based card play.
Inscryption leans a little harder on reads, though the gap is small.
Fallout: New Vegas
Scripted factions and enemies
Inscryption
Scripted opponents with light bluff moments, not true adaptation.
Inscryption leans clearly harder on variance.
Fallout: New Vegas
Some loot and crit RNG
Inscryption
Card draws and event choices randomized.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
Inscryption
Deck construction and sacrifice math drive victories.
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.