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
Fast mech duels testing piloting execution and prediction of human opponents.

Execution · Competitive PvP
Tactical gunfights testing aim, entry planning and prediction of human opponents online.
Mecha Break 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.
Mecha Break
Boost management and aim in fast mech duels demand dexterity
Tom Clancy's Rainbow Six: Vegas
Aim and snap-to-cover gunplay punish slow hands
Mecha Break leans a little harder on reads, though the gap is small.
Mecha Break
Human pilots adapt positioning and engage timing constantly
Tom Clancy's Rainbow Six: Vegas
Multiplayer angles and pushes demand reading human opponents
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mecha Break
Match conditions are mostly fixed beyond extraction-mode loot
Tom Clancy's Rainbow Six: Vegas
Terrorist hunt spawns vary modestly between runs
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mecha Break
Mech loadouts and role matchups reward roster knowledge
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.