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 · Competitive PvP
Substitution baiting against humans atop simple anime-fighter inputs and team picks.

Execution · Competitive PvP
A wrestling fighting game about timing grapples and reading opponents.
Naruto Shippuden: Ultimate Ninja Storm 2 leans Execution (Competitive PvP); Rumble Roses XX leans Execution (Competitive PvP).
Rumble Roses XX leans a little harder on execution, though the gap is small.
Naruto Shippuden: Ultimate Ninja Storm 2
Timing substitutions and combos matters but inputs are simple
Rumble Roses XX
Grapple timing and counters demand precise input
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Naruto Shippuden: Ultimate Ninja Storm 2
Versus humans, baiting substitutions is the real layer
Rumble Roses XX
Human opponents require reading attack and grapple timing
Rumble Roses XX leans a little harder on variance, though the gap is small.
Naruto Shippuden: Ultimate Ninja Storm 2
Nothing hidden once both characters are known
Rumble Roses XX
Some reversal and grapple randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Naruto Shippuden: Ultimate Ninja Storm 2
Team composition and chakra management have solvable lines
Rumble Roses XX
Move sets and match strategy reward planning
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.