I'd like to recommend NOT getting a miniDVD, CF or HD camcorder - the compression ratios on the film results in pixelisation when played back on tvs, particularly noticeable as you go up in tv size...
First, I assume that by HD you mean "hard disk" and not "Hi Def". Obviously, a high definition video camera is generally going to give you a much better picture than a standard def mini-DV camera.
As for the rest, be careful with generalizations. Excluding high definition cameras and non-digital cameras, there are several popular recording formats these days. Mini-dv and Digital8 both record with a format called DV but they use different media (mini-DV tapes and 8mm tapes). MiniDVD camcorders (and most of the tapeless camcorders) record using a format called MPEG2. A few now use MPEG4.
There is nothing inherently worse about MPEG2 or MPEG4 video as compared to DV, but there are advantages and disadvantages to each. First, the compression levels increase from DV to MPEG2 to MPEG4. That means that you can store more video using less data. If you try to compress too much, you get the pixelation effects referred to above. However, as examples that these are not problems inherent to the formats, all DVDs are MPEG2 (and many look quite nice) and many high definitions broadcasts shown via cable and satellite use MPEG4.
MPEG2 and MPEG4 are similar to using JPEG in that you can vary the amount of compression. If you compress too heavily, the picture gets really ugly. If you keep the compression moderate, you can get a lovely picture using much less space.
A big downside of MPEG formats comes when you edit them. Most frames in an MPEG video stream share their information with the frames before and after them. In order to display or render a frame, the computer has to actually process several frames. This isn't true with DV. So if you edit your videos, you'll need a lot more space with DV but the editor will work MUCH faster.
A big advantage to MPEG2 video is that it's what DVD players natively understand, so if you don't plan on editing and just want to get it onto a DVD, it's the easiest way to go.
Now even though there isn't an inherent picture quality disadvantage for MPEG2 and MPEG4 video, the camcorders currently on the market for those formats are clustered around the low end of the camcorder spectrum. I don't know of anyone making a particularly good MPEG2 or MPEG4 video camera. So the prior poster is essentially correct in saying that you should be very wary about non-mini-DV camcorders if image quality is particularly important to you.
Just be glad you aren't looking at high def camcorders. From what i can tell, all of the consumer ones use mini-DV tapes, but there are two competing standards (HDV and AVCHD). HDV isn't even a consistent standard with video from some manufacturer's camcorders being incompatible with others. You also have to worry about resolution (480, 720, or 1080 lines), whether you want to shoot interlaced, progressive, or pseudo-progressive, and what frame rate you want to shoot at (24fps, 25fps, 30fps, 50fps, or 60fps).
I'm shopping for a mini DVD for our upcoming trip, too.
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