I recommend tape for the simple fact that you can put it on a shelf in the least compressed mode for awhile (10 years). HDD means it is on your hard drive taking up space and prone to a head crash. Best backup for 13GB at a time? Tape.
DVD is compressed MPEG and editing it can be a chore, but new editors can edit MPEG-2 without lose. But, you need to get one that edits natively and not use a copy that you have had for 5 years. DVD is prone to skipping in extreme conditions, so handheld is OK, but handheld in the roller coaster would probably have issues (regardless of the vendor letting you on with a camera).
HDD AVC and AVCHD... just note that compression is way up and they are not yet using data rates that get the whole picture that they could. HDV (a tape format) does not compress as heavily.
The Canon HV-20 is a good price and a great picture. HD, but you can shoot DV IIRC. I recommend shooting HD and if you just want DV, let the camera do the downconvert to edit. Tapes are $ each time, but you have a copy.