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
Time-manipulation puzzles meet the series' signature weapon-upgrade gunplay.

Optimization · Practiced Mastery
The pioneering ninja stealth game of rooftop grappling and one-strike assassinations in feudal Japan.
Ratchet & Clank: A Crack in Time leans Optimization (Practiced Mastery); Tenchu: Stealth Assassins 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.
Ratchet & Clank: A Crack in Time
Hoverboot movement, aiming, and time-puzzle dexterity.
Tenchu: Stealth Assassins
Grapple movement and stealth-kill timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Ratchet & Clank: A Crack in Time
Entirely scripted single-player content.
Tenchu: Stealth Assassins
Guards patrol on fixed routes
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Ratchet & Clank: A Crack in Time
First-pass unknowns in puzzles and arenas.
Tenchu: Stealth Assassins
Item drops and unseen layouts first run
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Ratchet & Clank: A Crack in Time
Clank's time puzzles and weapon economy are solvable systems.
Tenchu: Stealth Assassins
Guard routes and Grand Master paths 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.