head to head
Neither is simply harder - they are hard in different places. Heroes of Might and Magic II demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Beloved fantasy turn-based strategy of heroes, castles, and stacked creature armies racing for map control.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Heroes of Might and Magic II leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Heroes of Might and Magic II
Turn-based clicking only
Portal
Portal placement timing modest.
Heroes of Might and Magic II leans clearly harder on reads.
Heroes of Might and Magic II
Hotseat duels reward mind games; AI is mappable
Portal
No adversary modeling player.
Heroes of Might and Magic II leans clearly harder on variance.
Heroes of Might and Magic II
Map exploration, morale, luck, and combat rolls
Portal
Deterministic chambers; no randomness.
Heroes of Might and Magic II leans a little harder on optimization, though the gap is small.
Heroes of Might and Magic II
Build orders, hero chaining, and creature math are deeply 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.