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

Optimization · Pure Optimization
A turn-based RPG where elemental surface interactions reward complete knowledge of combinatorial systems.

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.
Divinity: Original Sin leans Optimization (Pure Optimization); Fallout: New Vegas leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Divinity: Original Sin
Turn-based combat requires zero twitch; positioning is deliberate
Fallout: New Vegas
Shooter inputs with VATS assist
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Divinity: Original Sin
AI opponents use scripted priorities with no player modelling
Fallout: New Vegas
Scripted factions and enemies
Divinity: Original Sin leans clearly harder on variance.
Divinity: Original Sin
Elemental surface interactions contain hidden combinatorial space to discover
Fallout: New Vegas
Some loot and crit RNG
Divinity: Original Sin leans clearly harder on optimization.
Divinity: Original Sin
Elemental chain combos and initiative manipulation are systemically solvable
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.