I have the Rossos on my car and I have the Ps2's on my other. I have to say, the Pirellis hook up much better and hold the road better on cornering. I find the PS2's squeal slightly on some turns taken at higher speeds where as the Pirellis hold the road nicer.
On the other hand, you get what you pay for. All around the PS2's are a great tire. Pirellis are a superior tire. IMO