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

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

Optimization · Practiced Mastery
A slow dungeon crawl testing build planning and labyrinth knowledge over twitch skill.
Grand Theft Auto V leans Execution (Practiced Mastery); Lunacid leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Lunacid
First-person melee timing matters but stays deliberate
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Lunacid
Dungeon denizens follow fixed King's Field-style patterns
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.
Lunacid
Labyrinth secrets are unknown until uncovered
Lunacid leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Lunacid
Build stats, spell hunting and route knowledge dominate
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.