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

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

Optimization · Pure Optimization
An auto-battling deckbuilder about building a loop to defeat the Lich.
Fallout: New Vegas leans Optimization (Pure Optimization); Loop Hero leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Fallout: New Vegas
Shooter inputs with VATS assist
Loop Hero
Autobattler, almost no inputs.
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Fallout: New Vegas
Scripted factions and enemies
Loop Hero
Enemies follow scripts.
Loop Hero leans clearly harder on variance.
Fallout: New Vegas
Some loot and crit RNG
Loop Hero
Card draws and loot drops randomize.
Loop Hero leans a little harder on optimization, though the gap is small.
Fallout: New Vegas
Faction routing, perks, builds heavily rewarded
Loop Hero
Deck and tile placement reward deep optimization.
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.