head to head
Neither is simply harder - they are hard in different places. BattleTech demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Turn-based mech tactics where lance builds and heat math decide drawn-out slugfests.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
BattleTech leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
BattleTech
Turn-based; no physical inputs matter
Portal
Portal placement timing modest.
BattleTech leans a little harder on reads, though the gap is small.
BattleTech
AI lances follow exploitable scripted behavior
Portal
No adversary modeling player.
BattleTech leans clearly harder on variance.
BattleTech
To-hit rolls and component crits swing fights
Portal
Deterministic chambers; no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
BattleTech
Mech builds, heat management, and initiative play
Portal
Pure puzzle-solving optimization.
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.