head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Competitive PvP
Arena-fighter execution and couch-versus prediction across an enormous anime roster.

Execution · Competitive PvP
Arcade punch timing with counter prediction in human bouts.
Dragon Ball Z: Budokai Tenkaichi 2 leans Execution (Competitive PvP); Ready 2 Rumble Boxing leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball Z: Budokai Tenkaichi 2
Beam clashes, vanish timing and arena movement reward fast hands
Ready 2 Rumble Boxing
Punch timing, dodges and rumble combos reward quick hands
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
Ready 2 Rumble Boxing
Human bouts become feint-and-counter prediction
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
Ready 2 Rumble Boxing
Nothing hidden once boxers are learned
Dragon Ball Z: Budokai Tenkaichi 2 leans a little harder on optimization, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi 2
A 120-character roster of matchup and item knowledge
Ready 2 Rumble Boxing
Boxer matchups and rumble meter use are quickly mapped
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.