Most units are capable of paperless geocaching, which means information (i.e., instructions and hints) beyond the basic coordinates can be loaded into the handheld device before the user heads out to the trail. Geocaching.com requires a premium subscription for this service; Garmin-owned opencaching.com is free to use. Both communities offer smart-phone applications, as well.
Without going the paperless geocaching route, users will need to print the description and hints to help find the cache. Most newer units are capable of one-click paperless geocaching, while others require you to first download a GPX file and then import the file to their unit.
All units are water and impact resistant, giving them a distinct advantage over using a smart-phone with an application.
Portability is an important consideration. Some units, such as the Garmin eTrex and Dakota series, are very pocket friendly, while some DeLorme and Magellan devices are more of a handful.
Screen dimensions are a key factor in the overall size. Small, 2.2-inch screens, like those on the eTrex, are big enough for basic trail plotting and geocaching, but a larger 4.0-inch screen is much easier for reading a bigger area and interpreting topographic maps. The ideal balance is a device with the smallest exterior dimensions and largest screen size. Units such as the Garmin Montana provide a large touch screen in a minimal package.
To keep your options open, consider devices with a microSD slot that can be used for adding maps, such topographic, street, or water maps.
There are a variety of controls used, and each has its own pros and cons. A touchscreen is typically easy to use, though some may be more difficult when wearing gloves. A combination of touchscreen and hard buttons may be the most effective design. The eTrex devices use a tiny joystick that works fine when info is downloaded to the device, but entering numbers and letters can be tedious. With limited practice, a user could become comfortable and even adept at using any control method.
As a rule, handhelds use convenient AA batteries (alkaline or rechargeable NiMH), though the Garmin Montana line can also use a single lithium-ion battery. For most casual hikers, all units provide the power to guide for a full day, especially if the unit is shut off during breaks. Using rechargeable batteries might provide longer run time and carrying a spare set is recommended.