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

Optimization · Pure Optimization
Player-driven economy management across resource chains and market trades.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
MegaWorld leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
MegaWorld
Menu-driven building with no physical demand
Portal
Portal placement timing modest.
MegaWorld leans clearly harder on reads.
MegaWorld
Open-market trading against players adds light prediction
Portal
No adversary modeling player.
MegaWorld leans clearly harder on variance.
MegaWorld
Market swings carry some hidden information
Portal
Deterministic chambers; no randomness.
Portal leans clearly harder on optimization.
MegaWorld
Resource chains and placement economics are the core test
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.