450 is the sweet spot for me. I've got a friend list full of drivers that will hit the same tracks night after night in various themed 450pp cars. We all know the brake zones and corner speeds on sport soft tires (although occasionally we run comfort soft). Its enough power to keep things interesting and it allows wheel drivers to race alongside DS3 drivers without incidents.
I'm finding not a lot of people like racing much above 500 performance points. That's where a lot of the top performing street cars are. My favorite cars are in the 600-650pp range; (Super GT) Nismo Xanavi, Zonda R.
What's your preference?