head to head
Neither is simply harder - they are hard in different places. Ender Magnolia: Bloom in the Mist demands more execution; Grand Theft Auto V demands more reads.

Execution · Practiced Mastery
A metroidvania testing boss-pattern execution and ability-loadout planning.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Ender Magnolia: Bloom in the Mist leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Ender Magnolia: Bloom in the Mist leans clearly harder on execution.
Ender Magnolia: Bloom in the Mist
Boss dodge timing and aerial control gate progress
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Ender Magnolia: Bloom in the Mist
Bosses cycle scripted attack patterns
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.
Ender Magnolia: Bloom in the Mist
The map is fixed, just unexplored at first
Grand Theft Auto V
Some mission and lobby randomness.
Ender Magnolia: Bloom in the Mist leans clearly harder on optimization.
Ender Magnolia: Bloom in the Mist
Ability loadouts, upgrades and route knowledge shape the run
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.