head to head
Neither is simply harder - they are hard in different places. BattleBlock Theater demands more execution; Grand Theft Auto: San Andreas demands more optimization.

Execution · Practiced Mastery
A chaotic co-op platformer mixing precise jumps with friendly betrayal.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.
BattleBlock Theater leans Execution (Practiced Mastery); Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery).
BattleBlock Theater leans clearly harder on execution.
BattleBlock Theater
Precise jumps and tosses under pressure.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
BattleBlock Theater leans a little harder on reads, though the gap is small.
BattleBlock Theater
Versus mode adds light human chaos.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Grand Theft Auto: San Andreas leans a little harder on variance, though the gap is small.
BattleBlock Theater
Levels fixed.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Grand Theft Auto: San Andreas leans clearly harder on optimization.
BattleBlock Theater
Gem routes and weapon picks learnable.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
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.