5. Sync And Store

As with smartphones, the choice is between GPRS and EDGE or the new 3G speeds, EVDO and HSDPA. 3G devices tend to be bulkier - the HTC Tytan and the Palm 700p and 700w; the EDGE Palm 680 is considerably slimmer. If you collect email regularly, expect one to two days of battery life from an EDGE device (Blackberry models do rather better and can run for two or three days without needing to be recharged). 3G takes more power but what takes the most power is switching from 3G to GPRS and back as you travel from a strong to weak signal.

Wi-Fi is common on PDA phones but it's 802.11b rather than the faster and more power-hungry 802.11g. Several PDA phones have built-in GPS, including the HTC Artemis, the HP Mobile Messenger and the Mio A701. They usually come with a version of the TomTom software but other GPS applications are available for Windows Mobile, including the popular CoPilot.

Nokia's PC Suite for devices like the E62 doesn't run on Macs at all and on Windows it isn't as sophisticated as Palm Desktop or ActiveSync for Windows Mobile. Blackberry uses a version of Intellisync if you're not connecting to a Blackberry Enterprise Server; again it lags behind the two main sync applications. There's a wider choice of applications for synchronizing Palm and Windows Mobile devices, including some for the Mac.

Internal memory for PDA phones typically ranges from under 20 MB to around 100 MB, which is used for running the operating system, storing files and installing any new applications. If you plan to take many photos, play music or use GPS, you'll need a memory card. Check for non-volatile memory; Treos and Windows Mobile Pocket PC Phones use this to back up your contacts, files, settings and new applications so that you don't lose everything if the battery runs down (or you have to take it out to change the SIM or memory card).

The Treo 650 has a full-sized SD slot on the top but MiniSD slots are much more common and the latest HTC models have MicroSD slots. Thicker devices like the Palm 700w and the HTC Tytan have the slot on the side so it's easy to switch cards when you're done listening to music and you want access to your GPS maps. Plumping for the smaller MicroSD slot doesn't mean it will be any more accessible; thinner models like the HTC Artemis and the Nokia E62 put the slot under the battery so switching cards is more difficult.