Both MiniDV and Digital 8 record exactly the same signal, so there's no difference there. However, there might still be differences in the quality of the lens and the image sensor CCD. Generally a larger lens allows a sharper and brighter image (but not always). A larger CCD usually has better resolution (but not always). If you can determine that the MiniDV camcorder has a better lens or CCD than the digital 8 camcorder then it may be worth it. Don't switch because of the recording format though since they're identical.
thanks, the difference in lens is one has cari zeiss lens other does not.I believe the ccd is larger. trv 480 sony and dcr-hc21 sony are the two cameras