Nope its not the 32 channels that give the better accuracy.
WAAS and another one I can't remember the name of give the better height accuracy.
Because the sattelites are all basically right above you its hard to pinpoint your height.
The newer ones that normally have 32 channels recieve signals from base stations that they can use to calculate the height better.

So will a 32 channel one give better accuracy? I'm looking at getting one of these too :|

Unless height accuracy is of great importance to you, which it might very well be, a 16 channel 1 will do the job fine.
I have the one mike posted and although the longest i've had it going on battery is about 8 hours i think it does 20 or something.
It's also not failed me so far.
Gets a lock very quicly out in the open and never lost signal for me.
The more expensive one will have a better chance of getting you a signal in places like america with massive skyscrapers on both sides however(or in your house)

I would go for this one, Serious piece of kit for bluetooth recievers, Little bit expensive compared to the other 1 suggested but you get what you pay for :D BTT- 338:thumbs:

http://cgi.ebay.co.uk/GPS-Bluetooth-Nemerix-Receiver-16-Channels-New-BT77_W0QQitemZ5859139201QQcategoryZ4668QQrdZ1QQcmdZViewItem#ebayphotohosting

Get one that looks like that. I have it on my XDA Exec and on my Tungsten T3 before that.

Ive had it going for a 3hr journey on the batt in a rental car after it spent 6 months constantly on charge (its connected directly to the battery and hidden under my parcel shelf )

Much better than the one that actually comes with tomtom

...on my XDA IIs... which would be best one I could get??

Wanting something with a good battery life, so I can use it on foot aswell, but also able to plug into the car & keep charged while driving...

lookin on ebay, but I'm lost!!