I may have posted before...but I had a revelation.
Favorite: Nurburgring (those bumps and dips can be great for throwing a car into a slide once you learn them all)
Best: Nurburgring Reverse
Go and trip the timer to start the lap (otherwise I think the Replay camera won't show an external View) then turn around and do it backwards.
It is a lot more Uphill, and some of the turns that you kind of fly through on the normal run turn into excellent high angle, looooong drifts in reverse.
Now if only there was some way to get rid of that damn blinking red circle.