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

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

Optimization · Pure Optimization
Maximizing Emblem synergies and inherited skills to dismantle precisely scripted enemy maps.
Fallout: New Vegas leans Optimization (Pure Optimization); Fire Emblem Engage leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Fallout: New Vegas
Shooter inputs with VATS assist
Fire Emblem Engage
Turn-based; Engage ring timing is menu-driven not reactive
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout: New Vegas
Scripted factions and enemies
Fire Emblem Engage
Scripted enemy phases never adapt to player tendencies
Fire Emblem Engage leans clearly harder on variance.
Fallout: New Vegas
Some loot and crit RNG
Fire Emblem Engage
Hit and avoid stats tighten variance; Engage mechanics are reliable
Fire Emblem Engage leans a little harder on optimization, though the gap is small.
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
Fire Emblem Engage
Emblem pairing, skill inheritance, and unit positioning are exhaustively solvable
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.