I personally don't have first hand experience at owning coilovers, but i have driven a GT with bc's and the ride was really good and smooth.
i was a passenger in a mrk1 GT quite a few years ago with some old D2s and they where really hard, the car felt like it was bouncing/bobing everywhere!
i will be getting coilovers eventually but I'm happy with what i have and i can't justify the money for coilovers brand new.