head to head
Assassin's Creed Odyssey asks more than Grand Theft Auto V, and the gap is optimization.

Optimization · Practiced Mastery
Greek-flavored action RPG where build-crafting drives long-haul play.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Assassin's Creed Odyssey leans Optimization (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Grand Theft Auto V leans a little harder on execution, though the gap is small.
Assassin's Creed Odyssey
Parry and dodge timing required, not punishing.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans a little harder on reads, though the gap is small.
Assassin's Creed Odyssey
Mercenary AI scripted, not adaptive.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Odyssey
Loot tiers and mercenary spawns randomized.
Grand Theft Auto V
Some mission and lobby randomness.
Assassin's Creed Odyssey leans clearly harder on optimization.
Assassin's Creed Odyssey
Engravings, gear sets, builds deeply solvable.
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.