I've heard that Digital8 is better quality than minidv. Has something to do with the amount of physical space for the recorded area. But, only Sony (and maybe still Hitachi) sell Digital8 recorders. Everybody sells minidv recorders. I suspect that Digital8 is on the way out.
For sure, don't get a miniDVD recorder. Expensive, and you cannot view a recording until you "close" the disk. After being "closed", you can no longer record to that disk at a later time, even if there is still room on that disk. And quality isn't all that good. Certainly not as good as regular DVD recordings.