head to head
Neither is simply harder - they are hard in different places. Fallout: New Vegas demands more execution; Through the Darkest of Times demands more variance.

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

Optimization · Pure Optimization
Risk-budgeting resistance actions against historical events and probabilistic crackdowns.
Fallout: New Vegas leans Optimization (Pure Optimization); Through the Darkest of Times leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Fallout: New Vegas
Shooter inputs with VATS assist
Through the Darkest of Times
Turn-based planning with no physical component
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Fallout: New Vegas
Scripted factions and enemies
Through the Darkest of Times
The regime escalates on historical script, not by modelling you
Through the Darkest of Times leans clearly harder on variance.
Fallout: New Vegas
Some loot and crit RNG
Through the Darkest of Times
Raids, arrests and event outcomes roll against hidden odds
Fallout: New Vegas leans a little harder on optimization, though the gap is small.
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
Through the Darkest of Times
Balancing morale, funds and member risk is a solvable system
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.