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.

Execution · Practiced Mastery
Open-world Stone Age action game about hunting and conquering tribal outposts with tamed beasts.

Execution · Practiced Mastery
Open-world western about an outlaw forced to hunt down his old gang.
Far Cry Primal leans Execution (Practiced Mastery); Red Dead Redemption leans Execution (Practiced Mastery).
Far Cry Primal leans a little harder on execution, though the gap is small.
Far Cry Primal
Bow aim, melee timing, beast control under pressure
Red Dead Redemption
Dead Eye softens but gunplay still wants aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Far Cry Primal
Scripted tribal AI never models the player
Red Dead Redemption
Multiplayer skirmishes add light human prediction
Far Cry Primal leans a little harder on variance, though the gap is small.
Far Cry Primal
Wildlife encounters and patrol spawns are random
Red Dead Redemption
Ambient events and spawns vary mildly
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Far Cry Primal
Outpost routes, crafting economy, beast taming order
Red Dead Redemption
Mission approaches and economy 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.