What is the battery life like on these devices.
I personally have a PocketPC and the most cost effective solution is to buy a GPS attachment for about £40. But I am concerned about battery life as it only lasts about 4 hours and probably less if powering a GPS card.
Also I guess the dedicated devices are more weatherproof? You'd need some sort of waterproof case or bag for a PocketPC.
The software for PocketPC's looks better though with your position shown on colourful maps on a large screen. Some of the dedicated devices look a bit primitive with black & white screens, no map and little more than a grid reference.