RS3s are harsh, noisy, and traction during normal driving isn't great. They are horrible in the rain. If you are looking for tires that are great when you put some heat in them, the RS3s are for you.
PSS are grippier on the street, quieter, and less harsh. I haven't used them on the track so I can't speak to their characteristics when hot.
2008 IB E92 M3| BBS | KW | Arkym | Platte Forme A.G. | Active Autowerke | K&N | Fabspeed | Dinan | Evolve-R