Another difference: The PR3 rear tread suddenly disappears at the end...the PR2 will give plenty of warning.
This.
SE Ohio on the way to EOM in NC last year. Got up in the morning, eyeballed my tires like always, "Oh ya, good till next season!"
12 hours later after running mostly backroads all the way to NC I was VERY glad to hear Continental/Harpers had a special deal on tires for the event. They would've lasted the weekend (maybe), but sure wouldn't be making the trip all the way home.
The interesting bit was we weren't running that hard. At least I wasn't. Maybe 7/10ths, and I wasn't blasting out of corners.