head to head
Neither is simply harder - they are hard in different places. Mario + Rabbids Kingdom Battle demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Turn-based tactics where movement combos turn battles into solvable puzzles.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Mario + Rabbids Kingdom Battle leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Mario + Rabbids Kingdom Battle
Turn-based; no dexterity gate
Portal
Portal placement timing modest.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mario + Rabbids Kingdom Battle
Enemy AI follows predictable rules
Portal
No adversary modeling player.
Mario + Rabbids Kingdom Battle leans clearly harder on variance.
Mario + Rabbids Kingdom Battle
Hit chances are mostly deterministic percentages
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.
Mario + Rabbids Kingdom Battle
Movement chains and team-jump routing are puzzle-solvable
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.