head to head
Neither is simply harder - they are hard in different places. Baldur's Gate 3 demands more reads; The Binding of Isaac: Rebirth demands more execution.

Optimization · Systems & Chaos
A D&D CRPG where build optimization and dice variance dominate every encounter.

Variance · Systems & Chaos
A twin-stick roguelike won by recognizing which item combinations break the game.
Baldur's Gate 3 leans Optimization (Systems & Chaos); The Binding of Isaac: Rebirth leans Variance (Systems & Chaos).
The Binding of Isaac: Rebirth leans clearly harder on execution.
Baldur's Gate 3
Turn-based; no input dexterity.
The Binding of Isaac: Rebirth
Twin-stick aim and dodging matter but pace is forgiving.
Baldur's Gate 3 leans clearly harder on reads.
Baldur's Gate 3
Companions/enemies scripted, not adaptive to player modeling.
The Binding of Isaac: Rebirth
Enemies and bosses scripted; no adaptive opponent.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Baldur's Gate 3
Dice rolls, hidden checks, encounter RNG everywhere.
The Binding of Isaac: Rebirth
Item pools and room generation drive run identity.
Baldur's Gate 3 leans clearly harder on optimization.
Baldur's Gate 3
Builds, party comp, action economy fully solvable.
The Binding of Isaac: Rebirth
Item synergy knowledge defines whether runs snowball.
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.