i replaced my PS2 with PS3 (18 inch) a year ago (review pending
) and really like them.
subjective, but for me
wet : PS3 better than PS2
snow : PS2 better than PS3 (go figure!)
dry : PS2 better than PS3 (marginal but PS2 has better feel/breakaway characteristics as well as a slightly higher limit)
PS3 definitely are harder wearing, but take a few miles to warm up! (very slippy initially)
Id like to try the PSS which would be a bias towards performance (as opposed to ultimate wet weather grip)
PS2/PS3/PSS you arent going to go wrong