head to head
Neither is simply harder - they are hard in different places. Naruto Shippuden: Ultimate Ninja Storm 4 demands more optimization; Thief Town demands more reads.

Reads · Competitive PvP
Anime arena fighter where managing the substitution gauge is the real duel.

Reads · Pure Mind Games
A local-multiplayer stealth game about blending in and reading which figures are human.
Naruto Shippuden: Ultimate Ninja Storm 4 leans Reads (Competitive PvP); Thief Town leans Reads (Pure Mind Games).
Naruto Shippuden: Ultimate Ninja Storm 4 leans a little harder on execution, though the gap is small.
Naruto Shippuden: Ultimate Ninja Storm 4
Simple inputs; movement and substitution timing matter
Thief Town
Timed stab inputs matter but aren't the ceiling
Thief Town leans clearly harder on reads.
Naruto Shippuden: Ultimate Ninja Storm 4
Versus humans, baiting substitutions is the core game
Thief Town
Reading human players hiding among NPCs is the core
Thief Town leans a little harder on variance, though the gap is small.
Naruto Shippuden: Ultimate Ninja Storm 4
Minor support-assist chaos
Thief Town
Crowd of identical NPCs hides players, adding uncertainty
Naruto Shippuden: Ultimate Ninja Storm 4 leans clearly harder on optimization.
Naruto Shippuden: Ultimate Ninja Storm 4
Team composition and matchup knowledge
Thief Town
Little system to solve beyond the bluffing layer
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.