head to head
Neither is simply harder - they are hard in different places. Buster Bros. demands more execution; Grand Theft Auto V demands more reads.

Execution · Practiced Mastery
Arcade positioning and pop-order planning against deterministic bouncing balloons.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Buster Bros. leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Buster Bros. leans clearly harder on execution.
Buster Bros.
Dodging splitting balloons while firing demands precise positioning
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Buster Bros.
Balloons bounce on pure deterministic physics
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Buster Bros.
Weapon drops vary slightly per clear
Grand Theft Auto V
Some mission and lobby randomness.
Buster Bros. leans a little harder on optimization, though the gap is small.
Buster Bros.
Optimal pop order per fixed stage layout is learnable
Grand Theft Auto V
Heists, money loops, builds learnable.
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.