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

Execution · Practiced Mastery
The fastest mainline Souls, distilling the formula into aggressive boss duels.

Execution · Practiced Mastery
Shaving lap time through precise car control and solvable line and tuning choices.
Dark Souls III leans Execution (Practiced Mastery); Gran Turismo 5 Prologue leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
fast roll timing against aggressive scripted bosses
Gran Turismo 5 Prologue
Braking points and throttle control decide every lap time
Gran Turismo 5 Prologue leans a little harder on reads, though the gap is small.
Dark Souls III
PvP invasions exist but are optional
Gran Turismo 5 Prologue
Online racecraft adds light wheel-to-wheel prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
fixed encounters converge after first sight
Gran Turismo 5 Prologue
Tracks and physics are fixed and fully knowable
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
movesets and builds are fully mappable
Gran Turismo 5 Prologue
Tuning setups and racing lines are an engineering problem
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.