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
A PSP stealth-action side story following Altair's hunt for Templars on Cyprus.

Execution · Practiced Mastery
An open-city sequel deepening freeflow combat and predator gadget play.
Assassin's Creed: Bloodlines 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: Bloodlines
Simplified PSP combat and climbing demand little precision
Batman: Arkham City
Combo chains and counters need timing.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed: Bloodlines
Templar guards are entirely scripted
Batman: Arkham City
Enemies scripted, not adaptive.
Assassin's Creed: Bloodlines leans a little harder on variance, though the gap is small.
Assassin's Creed: Bloodlines
Compact fixed maps leave few surprises
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: Bloodlines
Route knowledge and counter timing are quickly solved
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.