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
An anime fighter testing combo execution and counter-baiting against human opponents.

Execution · Competitive PvP
An anime arena fighter testing team-switch timing and counter prediction against humans.
Dragon Ball Z: Budokai 3 leans Execution (Competitive PvP); One Piece: Burning Blood leans Execution (Competitive PvP).
Dragon Ball Z: Budokai 3 leans a little harder on execution, though the gap is small.
Dragon Ball Z: Budokai 3
Combo execution, teleport counters and beam timing demand hands
One Piece: Burning Blood
Combo timing and guard breaks need moderate hands
Dragon Ball Z: Budokai 3 leans a little harder on reads, though the gap is small.
Dragon Ball Z: Budokai 3
Versus humans, baiting teleports and guessing cancels decides exchanges
One Piece: Burning Blood
Human opponents bait switches and counters constantly
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 3
Almost nothing random beyond minor clash inputs
One Piece: Burning Blood
Full-information arena with no hidden state
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 3
Capsule builds and matchup knowledge underpin competitive play
One Piece: Burning Blood
Team composition and Devil Fruit matchups reward study
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.