For me, being a Brit living in the wetlands of Britain, the huge plus of the PR series is that the wet grip, even from stone cold, is not that far off it's grip in the dry.
I never used the 2 but heard great things about it.
The 3 is still the best all round tyre for our mixed weather (says he who hasn't used anything else since 2012).
I never liked the tramlining over broken, longitudinal tarmac joints with the 4 but for all-round UK confidence I doubt the PR's can be bettered and ain't about to spend my money finding out.
And, Chris, I thought I was the only one who threw away new tyres. The new Bridgestone BT014's that the previous owner of my K12S kindly put on for me between test riding it on heaven-knows-what and collecting it, almost killed me on too many occasions and they went in Micheldever Tyres' skip with 900 miles on them