Without going on detailed explanation, I can tell that Hard Disk (HDD) cameras are the better between these two, but the price is more. Both the cameras (HDD and DVD disk) uses MPEG-2 formats. For DVD disk cameras you can use mini DVD disks. These can normally record about 30 minutes (the best quality movie), but you can get more recording time, if you don't use the best movie quality. For HDD cameras your recording time depend upon the movie quality you select and the capacity of the Hard Disk. Normaly with a 30 GB camera you will be able to record 7 and a half hour at the best quality (more than 10 hours at a lower quality- which I think will satisfy your required quality).