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
Isometric co-op puzzling testing coordination and trap-room solutions.
Assassin's Creed Syndicate leans Optimization (Practiced Mastery); Lara Croft and the Temple of Osiris 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
Lara Croft and the Temple of Osiris
Twin-stick aiming and trap dodging take light skill
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
Lara Croft and the Temple of Osiris
Enemies swarm on fixed triggers
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
Lara Croft and the Temple of Osiris
Puzzle and trap layouts are fixed once seen
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
Lara Croft and the Temple of Osiris
Co-op puzzle solving and score routing lead the test
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.