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
Series finale blending stealth with active battlefields and heavy cinematics.

Optimization · Practiced Mastery
Routing guard patrols and executing clean stealth kills through fixed missions.
Metal Gear Solid 4: Guns of the Patriots leans Optimization (Practiced Mastery); Tenchu Z 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.
Metal Gear Solid 4: Guns of the Patriots
flexible gunplay alongside sneaking
Tenchu Z
Stealth-kill timing and movement control matter but forgive
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 4: Guns of the Patriots
battlefield factions act on scripts
Tenchu Z
Guard patrols are scripted, mappable routes
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 4: Guns of the Patriots
mid-battle chaos mostly cosmetic
Tenchu Z
Patrol routes are unknown only on first attempts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 4: Guns of the Patriots
camo, gear, and route knowledge per act
Tenchu Z
Routing each mission for undetected kills is the real game
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.