autocom every time for me.
Sure you have to fit the kit in the helmet, but its not too much of a pain, and if you really want to ,you could get them to do it for you
The clip-on bluetooth jobs seem pretty good for occasional use, but no good for trips that are more than a couple of days, and definitely no good if you want to make use of the satnav or mp3 player. Their batteries just don't last long enough.
Autocom have just released a wireless setup, but it seems they are still corded from the helmet to the 'hub', and I've not spoken to anyone who has one of these setups yet.
Note that they have a half price sale on for all the pre-2009 kit, so now is the time to buy if your looking