The fact is, PDAs often present as many problems as they solve. Gallivanting with an encyclopedia's worth of data in the palm of your hand has a romantic ring, but in reality, all too often the PDA's inherent limitations can get between you and your data. Its miniature display can be difficult to read. Input options such as handwriting recognition can turn something as simple as entering contacts into an arduous task. Some PDAs don't even offer a way to swap out the battery should the primary one die. The sheer number of PDA configurations and peripherals makes it essential for you to know exactly how much functionality your users will need to perform their mobile tasks. But to know this, you need to know your hardware options.

Choosing a platform
The two main PDA platforms are Palm and Pocket PC. Various vendors offer divergent models, each of which has its own strengths and weaknesses. The first step is to match required tasks with available options--such as input options (text recognition or thumbpads), connectivity (Bluetooth and/or Wi-Fi), and display type (monochrome or color).

Processors
Most early Palm-based devices run admirably on a 16MHz Motorola DragonBall CPU, while newer models like the Tungsten T use a zippier, 200MHz OMAP processor from Texas Instruments to support a color display, advanced functions such as Wi-Fi, and so on.

The first Pocket PCs shipped with a 206MHz StrongArm processor, which capably handled the original Pocket PC OS. Newer PDAs running Microsoft's improved Pocket PC 2002 OS are built around new CPUs--Intel's XScale, running at 300MHz and 400MHz--that facilitate functionality such as built-in Bluetooth and wireless networking. Although XScale is certainly faster, you can only harness its full performance by running applications optimized specifically for the XScale processor line; otherwise the general consensus is that XScale's performance is similar to that of the original StrongArm processor.

In general, though, the faster the processor, the more your users will be able to do. A 200MHz processor is probably adequate for most--if not all-- needs. However, if you're considering an XScale-based PDA, you may want to do some research to see whether the applications you're interested in are--or will be--available in XScale-optimized versions.

Input options
Both Palm OS and Pocket PC OS feature text recognition as an input option. Palm OS requires that you write "Graffiti"--a hieroglyphic version of the regular alphabet--which requires time to learn (although Graffiti 2, which promises improved usability, is on the horizon). Pocket PC OS offers more recognition flexibility in that you can input text in (mostly) regular block text and it will be deciphered; additionally, Pocket PC OS offers a tool called "Transcriber," which lets you write anywhere on the screen, in any style, and your writing is converted to text in an application. But to be fair, neither platform offers 100 percent recognition accuracy, and scribbling with a stylus on a miniscule, touch-sensitive screen isn't exactly conducive to productivity.

Some PDA models--such as Sharp's Linux-based Zaurus--feature Blackberry-type thumbpad keyboards, but these have tiny keys that take some getting used to, and they're not for everyone. Nevertheless, some users will need to do full-fledged data entry or document editing, and this is best accomplished via some kind of external keyboard. Targus' Stowaway models, for example, fit easily into a briefcase or suit pocket, yet are pretty much full-size when unfolded; Pocketop offers a wireless keyboard that connects to a PDA via the infrared port. Using a keyboard with a PDA is a good way to work on the road without having to lug a notebook PC, though it's important to note that third-party keyboards are generally designed for specific devices and aren't interchangeable.

Displays
While PDAs are still available with monochrome displays, most PDAs these days--aside from a few Palm/Handspring models--have color screens. If you merely need PIM functions such as contacts and calendar, PDAs with monochrome displays would be adequate and can certainly help you cut costs. But many users have more complex needs, especially those who read and send e-mail on the go. These users may need to view attachments, images, charts, or graphically rich documents, and such tasks usually require a color display.

Memory
All PDAs ship with a certain amount of built-in memory, usually broken down into flash ROM for the system software and flash RAM for applications and storage. On the low end, some Palm and Handspring devices ship with 8MB total memory, which is adequate for basic PIM functionality; at the other end of the memory spectrum, certain Pocket PC units now ship with 64MB, which is more suited for running resource-hungry mobile apps like Pocket Word and Excel, and provides ample storage space for data. And there are many models in between, with 16MB and 32MB capacities. But how much memory will be enough depends on how many applications you'll need, what kinds of applications you expect to run, and how much data storage you'll require.

Expansion
If 64MB isn't enough memory, most PDAs come with expansion slots (or add-on sleeves that have slots) that can accommodate either compact flash (CF), secure digital (SD), or multimedia memory (MMC) cards--sometimes all three. Storing extra data on these cards can free up internal RAM for applications, and many applications can be installed directly to a memory card. So instead of shelling out big bucks for the latest and greatest 64MB devices, you could pick up a fleet of 32MB models and add extra memory cards as needed.

Extra memory isn't the only expansion option. CF-based devices such as wireless modems are also available. Some PDAs can accommodate PCMCIA cards (usually via an expansion sleeve) or proprietary add-on cards (as with Handspring's Springboard), which makes available a wider range of devices, including network cards, modems (wired or wireless), GPS radios, and other devices.

Connectivity
Of course, you can synchronize your PDA with your desktop computer by popping the unit into its cradle, but connectivity doesn't have to stop there. Some higher end units offer built-in Wi-Fi and/or Bluetooth connections; for the rest, Wi-Fi and Bluetooth expansion cards (CF, PC, and Springboard) are available. With these capabilities, your users can roam (relatively) freely while still able to access the Web or the corporate network, or connect to other devices via their PDA. Infrared--or IrDA--ports are also available on most PDAs, but these have an extremely limited, line-of-sight range, really only useful for synchronizing data to a notebook PC or swapping business cards with another PDA user. Some models--such as HP's iPaq 3870 and Palm's Tungsten T--even let you establish a wireless Internet connection via a Bluetooth-enabled cell phone.

Battery life
Batteries and battery life have always been contentious issues for PDAs. Gone are the days when a Palm device could run for months on a pair of triple-A batteries. As users demanded more functionality like backlit screens, wireless connectivity, and other power-hungry options, PDA vendors added many of these functions to all but the most basic PDAs.

For example, a full charge to the lithium-polymer battery in Palm's new Tungsten T model--with its backlit, high-resolution color display, zippy processor, and built-in Bluetooth--lasts an average of one week. (This assumes about half an hour of use per day, with some--though not constant--use of Bluetooth.) Such performance apes the battery life of most Pocket PC devices.

Then there's the issue of charging the batteries. Some devices must be docked in their cradles to recharge, which could be inconvenient in some circumstances. More important perhaps is whether a PDA has a user-replaceable battery, so a spare can be popped in when the primary runs out. This issue is key, since some PDAs (early iPaq models, for example) have an internal battery that can be replaced only by the vendor should it wear out. And batteries do wear out.

There are steps that users can take to minimize power consumption, such as turning off the backlight and refraining from listening to MP3 music files. But if your users will be using their PDAs extensively--as notebook replacements, for instance--a replaceable battery (and several spares, for that matter) is a must.

Bottom line
Choosing the right PDA for your users isn't a simple task. To get the most for your money--and keep your users happy--you must find the right balance of utility and price. The good news is that viable choices are available in both the Palm and Pocket PC camps. The big issues--power, expansion, connectivity, ergonomics, input options, and battery life--have reasonable solutions. Do your homework, and choose wisely.

Which PDA is the ideal handheld for your staff? TalkBack below or e-mail us.

Todd Volz is an Associate Editor for ZDNet Tech Update.
Jonathan Blackwood is an educator, freelance writer, and editor living in Austin, TX.