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
A long Viking RPG carried by exploration and gear progression.

Optimization · Practiced Mastery
San Francisco hacker sandbox blending stealth, drones, and toy gadgets.
Assassin's Creed Valhalla leans Optimization (Practiced Mastery); Watch Dogs 2 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 Valhalla
Combat timing matters but forgiving.
Watch Dogs 2
Shooting and driving moderate input demands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Valhalla
Enemies scripted and predictable.
Watch Dogs 2
Enemy AI scripted; some PvP invasions exist.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Valhalla
Loot rolls and raid encounters vary mildly.
Watch Dogs 2
Hack outcomes and patrols vary mildly.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Assassin's Creed Valhalla
Skill tree, gear, raid routing solvable.
Watch Dogs 2
Gadgets, hacks, mission approaches 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.