head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

Variance · Grand Arena
A digital card game balancing opponent reads against draw variance.

Optimization · Grand Arena
A fast-format digital Yu-Gi-Oh! card game built around ranked PvP and meta decks.
Hearthstone leans Variance (Grand Arena); Yu-Gi-Oh! Duel Links leans Optimization (Grand Arena).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Hearthstone
Clicks only, no mechanical skill
Yu-Gi-Oh! Duel Links
Tapping cards, no dexterity test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Hearthstone
Human opponents bluff and adapt mid-match
Yu-Gi-Oh! Duel Links
Ranked PvP rewards predicting set cards and bluffs
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Hearthstone
Draw RNG and discover effects swing games
Yu-Gi-Oh! Duel Links
Draws and unknown opponent decks dominate
Yu-Gi-Oh! Duel Links leans a little harder on optimization, though the gap is small.
Hearthstone
Deckbuilding, mulligans, and mana curves matter
Yu-Gi-Oh! Duel Links
Meta deckbuilding and line calculation are the spine
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.