head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

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

Optimization · Practiced Mastery
Open-world Hyrule built on physics puzzles and exploration over reflex tests.
Assassin's Creed IV: Black Flag leans Optimization (Practiced Mastery); The Legend of Zelda: Breath of the Wild 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.
Assassin's Creed IV: Black Flag
Naval broadsides and boarding need modest timing
The Legend of Zelda: Breath of the Wild
Parry timing and aiming matter but forgiving.
Assassin's Creed IV: Black Flag leans a little harder on reads, though the gap is small.
Assassin's Creed IV: Black Flag
Multiplayer deception mode; campaign is scripted
The Legend of Zelda: Breath of the Wild
Enemies follow fixed scripted behaviors.
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
The Legend of Zelda: Breath of the Wild
Weapon drops and weather lightly randomized.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed IV: Black Flag
Ship upgrades and fleet economy drive progress
The Legend of Zelda: Breath of the Wild
Shrines, cooking, traversal routes fully solvable.
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.
full breakdown
Assassin's Creed IV: Black Flag →
full breakdown
The Legend of Zelda: Breath of the Wild →