Hi Kazumi
I would say that both models have and act totaly different upon spin.
The fixed central model when in a spin has no lateral movement, so if it spins, it spins.
Where as the moving central point, can shift the mass to one side, this will give a more vigorous spin but will allow the driver to find the direction of grip quicker.
(In a sim the mass moves from front to side to back, which makes a bigger spin turn then the fixed central point does)
Which is why in a game like (shift), you spin and its game over, where in a sim like (rfactor) you can save a spin and save the car.
In a different note, the other biggest difference between the two different models is that the four contact points can create the feeling of front, rear and four wheel drive (even three wheel)
(by shifting the mass and the central point of the car)
The fixed central point can only provide wheel spin and drift to simulate the difference between front and rear drive.
And dont get me started on wheels, tires and grip.
Thats a totaly different model.
(but as im not been paid or part of a racing company, I aint going to go into details of the why's and hows with them)
But trust me Pcars has not even touched the tip of the iceberg of what is provided in a sim regarding control, grip and turning.