The huge selection of GPS units can get confusing when considering the multitude of features that each provides. However, there are a few common traits shared between different types of GPS units that you should consider when purchasing a GPS.
Picking the best GPS for you depends on many factors, most importantly how you plan to use it. A handheld GPS will not do much good in a vehicle, and a GPS fish finder will not do much good on the trail. Because GPS units have different purposes, they will also have different features. However, all GPS units share a few common traits that you should look for when buying them.
Another factor to consider when determining how to pick the best GPS to buy is the map accuracy. All GPS units have to get their maps from somewhere, and depending on the manufacturer of a given GPS, the maps will come from either TeleAtlas or Navteq. Some people suggest that Navteq provides more accurate maps, at least in the United States, but the difference between the two is most likely very small. Fortunately, if you have a destination in mind that you plan on using your GPS unit at, you can check that destination at either Google or Yahoo maps. Google Maps use TeleAtlas, and Yahoo Maps use Navteq, which makes it easy to compare the accuracy of a given area between the two. TomTom GPS units are the primary user of TeleAtlas maps, while Garmin and most other GPS manufacturers use Navteq.
The POI (Points of Interest) database included with a GPS can be an important factor to consider when deciding which GPS is the best one to buy, especially if you plan on using it for travelling. A larger POI database means more locations such as restaurants, hotels, and scenic locations that your GPS will be able to show you. If the GPS you are considering has a small POI database, you can easily pay to upgrade it, or find a free database online, but it's easier just to choose a GPS with a large POI database pre-installed.
Screen Size and Resolution
Having a GPS really doesn't do any good if you can't see it, so the best GPS for you to buy should have a screen size and resolution that you are comfortable with. The screen size for most GPS units is between 1.5 and 6 inches diagonal, with resolutions ranging from 160x100 to 800x480. With a smaller screen, you'll need to be close to the unit to see anything, so larger screens are better for vehicles. The brightness of the screen is also a factor; if you plan on viewing the GPS in direct sunlight, you want a brighter screen.
There are tons of features specific to the different types of GPS units that you may also find important. For road navigation, you probably will want to look for a good 3d view, and text-to-speech support. For the trail, portability is probably one of the most important features. You also want to make sure that your GPS can be easily updated, and will be supported by the manufacturer in the long run.