head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Raiden V: Director's Cut demands more execution.

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

Execution · Practiced Mastery
Memorising scripted bullet waves and executing routes flawlessly for score.
Grand Theft Auto V leans Execution (Practiced Mastery); Raiden V: Director's Cut leans Execution (Practiced Mastery).
Raiden V: Director's Cut leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Raiden V: Director's Cut
Weaving bullet patterns demands precise sustained piloting
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Raiden V: Director's Cut
Enemy waves are fully scripted, nothing adapts
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Grand Theft Auto V
Some mission and lobby randomness.
Raiden V: Director's Cut
Patterns are fixed; surprises vanish after one credit
Raiden V: Director's Cut leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Raiden V: Director's Cut
Memorised routes and weapon choices define high scores
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.