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
Cold War-era shooter pairing twitch multiplayer with the cult Zombies mode.

Execution · Competitive PvP
Mobile shooter execution with human prediction, plus loot variance in battle royale.
Call of Duty: Black Ops leans Execution (Competitive PvP); Call of Duty: Mobile leans Execution (Competitive PvP).
Call of Duty: Black Ops leans a little harder on execution, though the gap is small.
Call of Duty: Black Ops
Gunfights hinge on aim and reaction speed
Call of Duty: Mobile
Touch or controller aim and movement decide gunfights
Call of Duty: Black Ops leans a little harder on reads, though the gap is small.
Call of Duty: Black Ops
Reading human opponents' positioning and timing
Call of Duty: Mobile
Human lobbies adapt rotations and peeks each match
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Black Ops
Spawns, care packages, zombies RNG
Call of Duty: Mobile
Battle royale drops and loot add run-to-run randomness
Call of Duty: Black Ops leans a little harder on optimization, though the gap is small.
Call of Duty: Black Ops
Class builds, map control, zombies routing
Call of Duty: Mobile
Loadout meta and map spawn knowledge 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.