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

Execution · Competitive PvP
Fast arena combat that tests combo execution and counter prediction against human opponents.

Execution · Competitive PvP
Tactical gunfights testing aim, entry planning and prediction of human opponents online.
Dragon Ball Z: Budokai Tenkaichi leans Execution (Competitive PvP); Tom Clancy's Rainbow Six: Vegas 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
Combo timing, dashes and beam clashes reward fast hands
Tom Clancy's Rainbow Six: Vegas
Aim and snap-to-cover gunplay punish slow hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball Z: Budokai Tenkaichi
Versus humans, predicting teleport counters and ki tactics matters
Tom Clancy's Rainbow Six: Vegas
Multiplayer angles and pushes demand reading human opponents
Tom Clancy's Rainbow Six: Vegas leans a little harder on variance, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi
Almost nothing random once movesets are known
Tom Clancy's Rainbow Six: Vegas
Terrorist hunt spawns vary modestly between runs
Tom Clancy's Rainbow Six: Vegas leans a little harder on optimization, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi
Character matchups and attribute builds are learnable systems
Tom Clancy's Rainbow Six: Vegas
Room-entry planning and map knowledge are studyable
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.