head to head
Neither is simply harder - they are hard in different places. Dragon's Dogma: Dark Arisen demands more optimization; Grand Theft Auto V demands more reads.

Optimization · Practiced Mastery
Build optimization and learned monster weak points, executed through physical climb-and-strike combat.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Dragon's Dogma: Dark Arisen leans Optimization (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Dragon's Dogma: Dark Arisen leans a little harder on execution, though the gap is small.
Dragon's Dogma: Dark Arisen
Climbing monsters and timing skills demands real combat dexterity
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Dragon's Dogma: Dark Arisen
Pawns and monsters follow learnable scripted behaviours
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon's Dogma: Dark Arisen
Bitterblack loot rolls and night spawns add managed randomness
Grand Theft Auto V
Some mission and lobby randomness.
Dragon's Dogma: Dark Arisen leans clearly harder on optimization.
Dragon's Dogma: Dark Arisen
Vocation builds, augment stacking and monster weak-point knowledge dominate
Grand Theft Auto V
Heists, money loops, builds learnable.
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.