CDR's are cheaper, able to Burn faster, in most Cases last longer and can be played/read on more devices (ie Portable Players, Older CDROMs)....CDRW's are resuable...Also I have yet to see a mini CDRW Disc (3") although I suspect they may be out there.
Edit= Forgot...CDR's are available in larger format's, hence can more Data can be burned on them.