head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Stories: The Path of Destinies demands more optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
Mapping a branching-fable decision tree with light combat between choices.
Grand Theft Auto V leans Execution (Practiced Mastery); Stories: The Path of Destinies leans Optimization (Practiced Mastery).
Grand Theft Auto V leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Stories: The Path of Destinies
Counter-based combat is forgiving Arkham-style timing
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Stories: The Path of Destinies
Enemies telegraph from fixed scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Some mission and lobby randomness.
Stories: The Path of Destinies
Branch outcomes are hidden until a path is tried
Stories: The Path of Destinies leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Stories: The Path of Destinies
Mapping choice combinations to find the true ending is the game
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.