head to head
Neither is simply harder - they are hard in different places. Might & Magic: Heroes VI demands more reads; The Elder Scrolls V: Skyrim demands more execution.

Optimization · Pure Optimization
A turn-based strategy game where building the optimal army and economy decides victory.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Might & Magic: Heroes VI leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
Might & Magic: Heroes VI
no real-time physical skill needed
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
Might & Magic: Heroes VI leans clearly harder on reads.
Might & Magic: Heroes VI
predicting human opponent strategy in PvP
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
Might & Magic: Heroes VI leans clearly harder on variance.
Might & Magic: Heroes VI
combat rolls and map resources random
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Might & Magic: Heroes VI leans a little harder on optimization, though the gap is small.
Might & Magic: Heroes VI
army building and economy near-solvable
The Elder Scrolls V: Skyrim
Skill stacking, enchant loops, and exploits are deeply solvable.
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.