There actually is a difference, because marketing folks (professional liars) are selling phones with Differential GPS. This doesn't use satellites at all but uses triangulation between towers and their known, fixed locations. It's not GPS at all, and IMHO, for them to sell it with the term GPS in the name should be fraud. Also saw it on Verizon as "eGPS". And to add insult to injury, it's a charge-per-use or limited subscription service thru Cingular/AT&T and still requires the purchase of software for some devices. Accuracy for these is demonstrably worse in any given location than a true GPS counterpart.

Adding on a real GPS receiver, or making sure the device has a SiRF type chip installed, gets you true satellite based GPS and at that point, your accuracy is as good as how many birds you can see-which is often dependent on how good the antenna is. the bluetooth enabled external GPS receivers are pricy, but usually effective. Tho again AT&T/Cingular locks some model phones so you can't use any old GPS application so you're stuck buying theirs and, guess what, paying a subscription fee.