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

Optimization · Practiced Mastery
Ezio rebuilds the Assassin order in Rome, with a cult-classic mind-game multiplayer attached.

Execution · Practiced Mastery
An open-city sequel deepening freeflow combat and predator gadget play.
Assassin's Creed Brotherhood leans Optimization (Practiced Mastery); Batman: Arkham City leans Execution (Practiced Mastery).
Batman: Arkham City leans a little harder on execution, though the gap is small.
Assassin's Creed Brotherhood
Kill-streak combat is stylish but easy
Batman: Arkham City
Combo chains and counters need timing.
Assassin's Creed Brotherhood leans a little harder on reads, though the gap is small.
Assassin's Creed Brotherhood
Hide-and-hunt multiplayer ran on human mind-games
Batman: Arkham City
Enemies scripted, not adaptive.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Brotherhood
Fixed campaign content
Batman: Arkham City
Fixed encounters and challenges.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Brotherhood
Recruit management and shop renovation economy
Batman: Arkham City
Gadget combos and challenge maps 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.