head to head
Fallout: New Vegas asks more than Dungeon Siege, and the gap is execution.

Optimization · Pure Optimization
A streamlined click-along action RPG famous for its seamless world.

Optimization · Pure Optimization
A faction-driven RPG-shooter where build and route planning shape every ending.
Dungeon Siege leans Optimization (Pure Optimization); Fallout: New Vegas leans Optimization (Pure Optimization).
Fallout: New Vegas leans clearly harder on execution.
Dungeon Siege
Combat mostly resolves itself
Fallout: New Vegas
Shooter inputs with VATS assist
Fallout: New Vegas leans a little harder on reads, though the gap is small.
Dungeon Siege
Mobs charge on simple scripts
Fallout: New Vegas
Scripted factions and enemies
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dungeon Siege
Loot drops vary modestly
Fallout: New Vegas
Some loot and crit RNG
Fallout: New Vegas leans clearly harder on optimization.
Dungeon Siege
Party builds and pack-mule logistics are the game
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.