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
Arena-fighter execution and couch-versus prediction across an enormous anime roster.

Execution · Competitive PvP
Substitution baiting against humans atop simple anime-fighter inputs and team picks.
Dragon Ball Z: Budokai Tenkaichi 2 leans Execution (Competitive PvP); Naruto Shippuden: Ultimate Ninja Storm 2 leans Execution (Competitive PvP).
Dragon Ball Z: Budokai Tenkaichi 2 leans a little harder on execution, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi 2
Beam clashes, vanish timing and arena movement reward fast hands
Naruto Shippuden: Ultimate Ninja Storm 2
Timing substitutions and combos matters but inputs are simple
Dragon Ball Z: Budokai Tenkaichi 2 leans a little harder on reads, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi 2
Versus friends, baiting transformations and dodges matters
Naruto Shippuden: Ultimate Ninja Storm 2
Versus humans, baiting substitutions is the real layer
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball Z: Budokai Tenkaichi 2
Full movesets are public knowledge
Naruto Shippuden: Ultimate Ninja Storm 2
Nothing hidden once both characters are known
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball Z: Budokai Tenkaichi 2
A 120-character roster of matchup and item knowledge
Naruto Shippuden: Ultimate Ninja Storm 2
Team composition and chakra management have solvable lines
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.
full breakdown
Dragon Ball Z: Budokai Tenkaichi 2 →
full breakdown
Naruto Shippuden: Ultimate Ninja Storm 2 →