Pirelli rear tyres last about 25%-50% as long as any of the competitors tyres, at a higher cost.
I back to back tested Pirelli Supercorsa SC SC1 against Bridgestone V02 Soft and Dunlop KR soft. Was within a tenth of each other (obviously adjusted bike setup for each tyre). The Bridgestone and Dunlop rears managed two days, with negligible performance drop. The Pirelli lasted half a day, noticeable performance drop after six laps, sliding everywhere in the last session before lunch.
The Pirelli was the fastest tyre, by one tenth. So, if you have good tyre budget (and enjoy wheel changes), go for the P.
When I did endurance racing, you had to put a new P in every session, or you weren't racing! B would do the whole race, plus a test day.
When I did BSB, same deal, new rear every session. P fronts are great though, easily as good as the Dunlop.