Mini DV camcorders provide the highest quality and allow you to retain that quality while you edit your video. Most modern computers and 99.9% of video editing software support DV. Windows XP comes complete with Windows Movie Maker, a basic editing software program. It has been cynically commented that Sony continues to make Hi-8 and digital 8 camcorders so that it can sell its stock of tapes.

Most camcorders now seem to have the DV input enabled. The reason older ones didn't (in Europe) was because of tax and import regulations. DV-in lets you put edited material (from your computer) back on to mini DV tapes. Some sellers will tell you that you can enable DV-in yourself - but not all camcorders can be converted, the process is not trivial, and you may have to pay for software and a cable to do it. Also enabling DV-in yourself may invalidate the camcorder's warranty. It is not worth the bother; just check that your chosen camcorder is DV-in enabled before you buy it. Others argue that if you intend to author to DVD the ability to copy back to tape is pointless. If you have got the facility and don't use it there is no problem. If you haven't then you are stuck on the occasions that you do need it

Movies shot in low light are grainy, lack contrast, provide poor colour rendering, and are generally of low quality. When manufacturers quote a particular low-light capability they never state what they consider is an acceptable picture in the given low-light condition; so you can never compare like-with-like. Zero Lux or Nightshot shots look terrible (well they do to me) and only work up to a few meters from the camcorder.

All domestic camcorders offer this facility; just ignore the salesman if he tries to sell a camcorder on this feature. Digital zoom simply enlarges each pixel of the picture, so the resulting quality is poor. The greater the digital zoom gets, the worse the quality gets. With DV out and in, it is easy to transfer material to a computer and use software to zoom in and out of the picture. The results are sometimes no better but it gives you a choice.

All mini DV camcorders provide 10x or higher optical zoom. High quality lenses that go much greater than this are expensive (professional lenses cost more than the average camcorder) so don't choose your camcorder on this basis. Unless you're prepared to carry around a robust tripod with you and use it, anything shot at greater than about 5x optical zoom will be very unsteady i.e. of poor quality. For good pictures a tripod is a must; this is true for any filming at any zoom level.

Unless you're buying for a particular purpose such as covert recording or for some extreme sport don't buy on the basis of the smallest size. It is usually easier to get steady pictures with the bigger camcorders. This is always a compromise and obviously considered on an individual basis. See comments about using a tripod above. Additionally as the camcorders get smaller the controls become smaller and are squashed closer together.

The audio of most DV camcorders is more than adequate but at some point, unless you just plan to record the family Christmas get together, you will probably need to plug in an external microphone. Check what input facilities the camcorder offers. Try to download a user manual before you buy.

Depending on how much you want to spend something that I would look for is the ability to switch options to manual, especially the focus, and how easy it is to do so.
Without trying each particular model it is difficult to make comments about which is preferable to which. Even with more professional cameras it can sometimes come down to brand loyalty. Some prefer Sony to Panasonic and one persons fault is another's feature. With most similarly priced camcorders you would need to compare the pictures side by side on an edit suite to notice much difference. The main problem in deciding is whether you find the features that you need easy to use. Not buried under several layers of menus or with a fiddly switch. Unfortunately this makes choosing your second camera easier than your first. To get round this do a search on the internet user groups for your short listed camcorders. If you read enough you should be able to weed out the extreme opinions and get a reasonable view from people who have already spent their money. If there are any undesirable features someone will have probably run into them.

One final note. Some of the small camcorders load the tape from underneath. This could mean that to insert or remove the tape the tripod attachment plate would need to be removed. This may or may not be a problem for you, but it is worth checking before you buy.