How big should you go? For years, 4.3-inch GPS screens were the standard, and some cheap GPS navigators still have them. However, most car GPS systems now have 5-inch screens that are easier to read at a glance. Bigger 6- and 7-inch screens are available, but experts say these can block a sizable chunk of the windshield; they're best suited to very large vehicles like full-size pickups.
Voice commands can make navigation safer. This is one frill that's really helpful. Upper-tier car GPS systems work by voice commands, so you won't have to take your hands off the wheel. Expect to pay about $200 for a voice-command navigator, though.
What maps do you need? Basic car GPS systems come with preloaded maps of the lower 48 states. Step-up models add maps of Alaska, Hawaii, Canada, etc., and they usually don't cost much more -- but the model numbers are always similar, so double-check that you're getting the right maps.
Are map updates included? It's smart to buy a car GPS system that includes free map updates for the life of the unit, experts say. It'll add maybe $20 to the price -- but a map update costs $30 to $50 otherwise.
Do you need traffic alerts? Free traffic alerts usually cost just a little extra on budget navigators (high-end units automatically include them). These work well in tests, steering users clear of traffic jams -- but only on major highways. On city streets (even in major cities like New York) and side roads, GPS systems usually have little traffic information. If you don't drive in well-covered areas -- or you rely on a smartphone app like Waze for your traffic info -- you may be able to skip this feature.
Will you use fancy routing features? These really can be timesavers, but you'll only find them on $150-plus navigators. For example, Auto Sort can take a bunch of stops (dry cleaners, day care, Chinese takeout) and sort them into one efficient route. Trip Planner lets you sort stops manually, setting your own departure and arrival times. Budget car GPS systems give you less control over your route -- but they'll still get you from Point A to Point B, and some owners prefer that kind of simplicity.