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

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

Execution · Practiced Mastery
Drilling fixed enemy movesets until parry-perfect execution carries a run.
Gran Turismo 5 Prologue leans Execution (Practiced Mastery); Sifu leans Execution (Practiced Mastery).
Sifu leans a little harder on execution, though the gap is small.
Gran Turismo 5 Prologue
Braking points and throttle control decide every lap time
Sifu
Parry and dodge timing on tight windows is everything
Gran Turismo 5 Prologue leans a little harder on reads, though the gap is small.
Gran Turismo 5 Prologue
Online racecraft adds light wheel-to-wheel prediction
Sifu
Enemies attack from fixed movesets, never adapt
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Gran Turismo 5 Prologue
Tracks and physics are fixed and fully knowable
Sifu
Levels are deterministic once learned
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Gran Turismo 5 Prologue
Tuning setups and racing lines are an engineering problem
Sifu
Learning movesets, shortcuts and the aging economy is the meta
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.