I want to give my opinion on this matter (might be a bit long):
Some friends and I, run street cars at 450PP with sport tires with FF, FR, 4WD, MR and RR enabled. 3 of my favorite cars are the MR2 '97 and the 190E 2.5 '91 and the AE86. We used to have such great races because we pick cars that are from the year 2000 or older to avoid M3, Elises, NSX, RX-8, 86 GT and all the "noob" cars or "god" cars that people tend to pick when they need a win. We race to have great battles and have fun.
With patch 2.10 we no longer can open a public lobby with the old settings. Now, we can only do FF + 4WD or FR only or MR only. Why? Because since my 450PP 190E is now 393PP I can simply add parts to make it 450PP again and win every single race even if I'm not trying. PD messed up big time. My MR2 did not change at all. When compared the 2 cars after the patch at 450PP the 190E is 2-3 seconds faster when before they were fairly even.
It's true, a car is not suited for all tracks. A 190E might do really good at Monza, Suzuka and GP/F but at Madrid, Monaco and London it will not since those tracks have many corners with few straights. Best thing you can do is set up the car and drive/race the best you can. Granted, some people say the patch 2.10 is great because you can now beat an NSX with a CL 600 on circuits you could only dream before.
The change has helped big time for higher PP ranges, I would say 500PP and above. For people who race with lower PP (450PP and lower) the game is broken now. We tried a "normal" race at Laguna Seca at 450PP. While many were using EG's, EK's, 22b, Evo's and such, one of my friends picked the SILEIGHTY (that had it's PP reduced by 50PP) and when the race started he didn't move the car until 20 seconds after everyone had started. He passed all of us in no time and crossed the finish line with 18 seconds to spare in 5 laps!!
Since his car dropped 50PP all he did was to add parts to make it again 450PP but in reality it was a 500PP under 2.09. Now, while everyone that likes to race with 550PP+ sees variety of cars, we on the other end see fewer cars because FR's are just too powerful vs FF's and 4WD's.
Instead of reducing the old cars PP they should have increased the "god" cars such as NSX, M3 and Elises so that way people would have to lower their PP even more making the races more even.
2.09 was fine, PD just needed to nerf the newbie cars, not the ones we actually have to spend a lot of time tuning so it doesn't oversteer at every corner. Or at least ask an admin to make a poll to see if people like or dislike the new PP system.