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

Execution · Practiced Mastery
Tests cautious route planning and scavenged-resource management through hostile zones.

Execution · Practiced Mastery
Open-world western about an outlaw forced to hunt down his old gang.
Left Alive leans Execution (Practiced Mastery); Red Dead Redemption leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Left Alive
Clunky shooting and stealth still demand careful manual play
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.
Left Alive
Enemy patrols run fixed detection scripts
Red Dead Redemption
Multiplayer skirmishes add light human prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Left Alive
Patrol layouts are unknown on first approach
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.
Left Alive
Crafting, routing and survivor choices reward planning over reflexes
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.