head to head
Neither is simply harder - they are hard in different places. Might and Magic VII: For Blood and Honor demands more variance; Portal 2 demands more execution.

Optimization · Pure Optimization
An open-world party blobber where promotion paths and skill routing matter far more than aim.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Might and Magic VII: For Blood and Honor leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Might and Magic VII: For Blood and Honor
Pausable party combat; minimal dexterity.
Portal 2
Portal placement requires some precision but timing is lenient.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Might and Magic VII: For Blood and Honor
Enemies charge on fixed logic.
Portal 2
No opponent; puzzles are static.
Might and Magic VII: For Blood and Honor leans clearly harder on variance.
Might and Magic VII: For Blood and Honor
Loot rolls and unknown dungeon contents first time.
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans a little harder on optimization, though the gap is small.
Might and Magic VII: For Blood and Honor
Class promotions, skill points, and routing are fully solvable.
Portal 2
Solving the puzzle's logic IS the entire game.
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.