head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Practiced Mastery
Twin assassins seize Victorian London borough by borough with gang warfare and a rope launcher.

Optimization · Practiced Mastery
A cinematic action adventure retelling Journey to the West in a post-apocalypse.
Assassin's Creed Syndicate leans Optimization (Practiced Mastery); Enslaved: Odyssey to the West 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 Syndicate
Rope-launcher traversal and simple brawling
Enslaved: Odyssey to the West
Forgiving combat and automated climbing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Syndicate
Gangs are scripted
Enslaved: Odyssey to the West
Mechs are scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Syndicate
Fixed activities
Enslaved: Odyssey to the West
Encounters fully fixed
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Syndicate
Gang upgrades and borough takeover planning
Enslaved: Odyssey to the West
Upgrades and encounter solutions are 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.