head to head
Neither is simply harder - they are hard in different places. Deadly Premonition 2: A Blessing in Disguise demands more variance; Fallout: New Vegas demands more execution.

Optimization · Pure Optimization
The sequel-prequel sends Agent York skateboarding around a Louisiana town to solve another surreal murder case.

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.
Deadly Premonition 2: A Blessing in Disguise leans Optimization (Pure Optimization); Fallout: New Vegas leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Deadly Premonition 2: A Blessing in Disguise
Skateboarding and light combat ask little of the hands
Fallout: New Vegas
Shooter inputs with VATS assist
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Deadly Premonition 2: A Blessing in Disguise
Enemies are scripted nuisances, never adaptive
Fallout: New Vegas
Scripted factions and enemies
Deadly Premonition 2: A Blessing in Disguise leans clearly harder on variance.
Deadly Premonition 2: A Blessing in Disguise
Unknown town events and clues on a first investigation
Fallout: New Vegas
Some loot and crit RNG
Fallout: New Vegas leans a little harder on optimization, though the gap is small.
Deadly Premonition 2: A Blessing in Disguise
Daily scheduling, crafting, and routing are the real systems
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.