"better" is an easy term to throw out there for discussion... and since the video files from HDD and flash are the same, what constitutes "better"?
When I am in a miniDV tape environment, I shoot video, fill the digital tape after about an hour (~63 or 83 minutes, depending on the tape length - never shoot using LP mode), take the tape out, lock it, make a note what is on the tape, put in another tape, resume shooting. I usually have an 8-pack of tape in the car - and another 8-pack in the gig bag. When I am ready to edit, I connect the camcorder to the computer using firewire, put a tape in the camcorder, rewind, import the digital video stream, take the tape out and store it in a cool dry place, edit the video on the computer, export the project back out to the camcorder (it is fun to watch in high definition by connecting the camcorder to a HDTV), burn a standard definition DVD if I want to share with others or export to a video data file (720p high definition) for upload to vimeo.com or YouTube. A year or three or five or more, I can pull digital miniDV tapes from the archive and use or re-use footage for another project if I want.
When I am in a Hard disk drive (HDD) environment, I shoot video, fill the hard drive after several hours (depends on the video quality selected, but shooting in highest quality is always recommended). In the unlikely event that I fill the hard drive before transferring any video, I either stop capturing video or start deleting things that have not yet transferred to a computer. When I am ready to edit, I connect the camcorder to the computer using USB (some JVC HDDs use firewire), mount the drive like any other mass storage device, copy the video files to the computer hard drive, and copy the files to yet another hard drive on the computer or start burning data DVDs for back-up. Optical discs are not considered an appropriate archival media. Edit the video on the computer. While it is apparently now possible to export the finished project back out to the camcorder (I believe Sony now allows for this) and use the camcorder as the playback device, that file will be "transient" - that is, the camcorder is not a place you want to store that file because it will be using room you would normally want to use for video capture activities... then, burn a standard definition DVD if I want to share with others or export to a video data file for upload to vimeo.com or YouTube. If I saved the DVD discs or the hard drive with the data file copies, then a year or three or five or more, I can pull digital data files from the archive and use footage that was cut from the original edit for another project if I want. If I decided that making a backup was not necessary and there is no archive, then the footage is gone forever. Hopefully the discs are OK and the hard drive has not failed. The time I thought I saved because copying over USB is faster than real-time transfer over firewire will mostly get eaten by the file copying activity. With a 60 minute miniDV tape at ~13 gig per hour of standard definition video or 44 gig per hour of high definition video, it continues to be a very inexpensive storage solution. The known issues with vibration and altitude with HDD cams have already been stated, so no repeat here.
Flash memory has a similar process flow to HDD. Since the file types and compression used by HDD and flash memory camcorders is the same, the video quality will be the same (and not as good as miniDV tape). While flash memory has the advantage of being a removable media, the memory cards are not recommended for a long-term storage/archive media and the $/gig is still expensive when compared to miniDV tape. Yes, flash memory cards are smaller than miniDV tape.
For consumer flash memory, high definition, camcorders, the list is pretty short. The Canon HF "family", Sony HDR-CX12 and Panasonic HDC-SD100. You mentioned the Sony HDR-UX20 in your first post - I would not touch a DVD based consumer camcorder and suggest you drop this from your short list.
In any case, all the consumer camcorders in this range regardless of the storage media used, have lenses and imaging chips that are larger than the consumer camcorders that are less $ - so that is the good news... but their imaging chips and lenses are still not as large as the next step up in the prosumer or low-end pro range.