Today manufacturers offer a number of high definition formats for consumer and prosumer videomakers. The knowledgeable folks at Videoguys.com recently created this handy .pdf to clarify the relative advantages and disadvantages of each format.
One thing you'll probably notice is that as HD formats become more compressed, as for example with AVCHD, the demands on your computer to edit the footage increase substantially. In some cases, transcoding the footage to a more easily editable format is in order. But that adds time and steps to your workflow.
Were I to purchase an HD camcorder today, I'd probably go with HDV. Since it uses tape, archiving source footage is cheap and reliable. And HDV editing is less taxing on a computer when edited allowing me to work with a more affordable machine. Most HDV cameras also shoot DV so if you want to shoot an SD project, that's easy enough to do.