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
Fast arena combat that tests combo execution and counter prediction against human opponents.

Execution · Pure Mechanics
Tests raw aim and movement speed in fast classic arena deathmatch.
Dragon Ball Z: Budokai Tenkaichi leans Execution (Competitive PvP); Half-Life Deathmatch: Source leans Execution (Pure Mechanics).
Half-Life Deathmatch: Source leans a little harder on execution, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi
Combo timing, dashes and beam clashes reward fast hands
Half-Life Deathmatch: Source
Aim, bunny-hopping and snap reactions decide duels
Dragon Ball Z: Budokai Tenkaichi leans a little harder on reads, though the gap is small.
Dragon Ball Z: Budokai Tenkaichi
Versus humans, predicting teleport counters and ki tactics matters
Half-Life Deathmatch: Source
Predicting human movement and spawn timing matters
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
Almost nothing random once movesets are known
Half-Life Deathmatch: Source
Fixed maps and item timers, little randomness
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
Character matchups and attribute builds are learnable systems
Half-Life Deathmatch: Source
Weapon spawns and map control are learnable systems
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.