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

Optimization · Practiced Mastery
An open-world pirate adventure where upgrading the Jackdaw matters more than the blade.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Assassin's Creed IV: Black Flag 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 IV: Black Flag
Naval broadsides and boarding need modest timing
Grand Theft Auto V
Driving and shooting demand decent inputs.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed IV: Black Flag
Multiplayer deception mode; campaign is scripted
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 IV: Black Flag
Weather, convoys, and hunting spawns
Grand Theft Auto V
Some mission and lobby randomness.
Assassin's Creed IV: Black Flag leans clearly harder on optimization.
Assassin's Creed IV: Black Flag
Ship upgrades and fleet economy drive progress
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.