I've got a PR3 on the back and it's a big improvement on the BT 21 I had on previous, the back end feels less twitchy under heavy braking. The BT 23 on the front is starting to square off, i'll stick with the pr3s if i get the chance when I renew.
Treat everything in life the way a dog would- if you can't eat it or foc it, forget it.