head to head
Neither is simply harder - they are hard in different places. Digital Devil Story: Megami Tensei demands more variance; Fallout: New Vegas demands more execution.

Optimization · Pure Optimization
Charting brutal mazes and solving demon-fusion math in a first-person crawler.

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.
Digital Devil Story: Megami Tensei leans Optimization (Pure Optimization); Fallout: New Vegas leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Digital Devil Story: Megami Tensei
Turn-based dungeon menus need no dexterity
Fallout: New Vegas
Shooter inputs with VATS assist
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Digital Devil Story: Megami Tensei
Demons follow fixed negotiation and combat rules
Fallout: New Vegas
Scripted factions and enemies
Digital Devil Story: Megami Tensei leans clearly harder on variance.
Digital Devil Story: Megami Tensei
Unmapped mazes and encounters punish until charted
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.
Digital Devil Story: Megami Tensei
Demon fusion math and maze mapping dominate progress
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.