R888 is a "rounder" tire/profile than the more square and stable AD08. AD08 is thus more stable but the R888 is an R-comp and a stickier tire. The RA1 has a square profile and is an R-comp and a great tire. Better than both in the rain when new and about the same as the R888 when worn to a slick.
IMO the AD08 and PS2 were fairly similar with the AD08 just edging it out, but i've never driven on the PSS to compare but it should be a lot better than the PS2.
Why not go with a Nitto NT01? I'd probably take a 275 NT01 over a 295 R888/PSS/AD08.