This is actually a tough question - I ride North OC all the time, Fullerton/Yorba Linda, SART, Carbon Canyon, Santiago Canyon etc. I think there are good elements about all of those routes, but none are very memorable now that I think about it. I agree that Carbon Canyon is overrated. When I want a great ride and have time to spend I find myself going to Santa Monica/Malibu for the canyons or to GMR or Angeles Crest. We just got back from Napa - wish we had roads like that in the OC.