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
Class-based team shooter with deep mind games.
Mecha Break leans Execution (Competitive PvP); Team Fortress 2 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
Team Fortress 2
Projectile aim and rocket jumps reward hands
Team Fortress 2 leans a little harder on reads, though the gap is small.
Mecha Break
Human pilots adapt positioning and engage timing constantly
Team Fortress 2
Spy/sniper duels are pure prediction
Team Fortress 2 leans a little harder on variance, though the gap is small.
Mecha Break
Match conditions are mostly fixed beyond extraction-mode loot
Team Fortress 2
Random crits and spread inject RNG
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
Team Fortress 2
Class loadouts and map routes solvable
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.