head to head
Neither is simply harder - they are hard in different places. CrossCode demands more optimization; Grand Theft Auto V demands more reads.

Optimization · Practiced Mastery
Retro-styled action RPG mixing fast combat with dense ball-physics puzzles.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
CrossCode leans Optimization (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
CrossCode leans a little harder on execution, though the gap is small.
CrossCode
fast ball-throwing combat and dash puzzles
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
CrossCode
no adaptive opponent
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Grand Theft Auto V leans a little harder on variance, though the gap is small.
CrossCode
content is fixed and scripted
Grand Theft Auto V
Some mission and lobby randomness.
CrossCode leans clearly harder on optimization.
CrossCode
element puzzles and builds reward systematic play
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.