head to head
Gran Turismo 5 Prologue asks more than Grand Theft Auto: San Andreas, and the gap is execution.

Execution · Practiced Mastery
Shaving lap time through precise car control and solvable line and tuning choices.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.
Gran Turismo 5 Prologue leans Execution (Practiced Mastery); Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery).
Gran Turismo 5 Prologue leans clearly harder on execution.
Gran Turismo 5 Prologue
Braking points and throttle control decide every lap time
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Gran Turismo 5 Prologue leans clearly harder on reads.
Gran Turismo 5 Prologue
Online racecraft adds light wheel-to-wheel prediction
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.
Gran Turismo 5 Prologue
Tracks and physics are fixed and fully knowable
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Gran Turismo 5 Prologue leans a little harder on optimization, though the gap is small.
Gran Turismo 5 Prologue
Tuning setups and racing lines are an engineering problem
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.