It used to be that when you were driving along in unfamiliar territory that you'd call on the carbon-based lifeform occupying the passenger's seat to call out directions from a paper map, or just drive around aimlessly for hours trying to reach your final destination (that is if you were too “above it all” to stop and ask for directions).

Today, we have GPS units that give visual turn-by-turn directions, speak street names, and provide real-time traffic information to always give you the fastest route to your destination. For those that don't require all of the visual stimulation of a “traditional” GPS unit, there's always GM's OnStar service.

These days, I lump GPS units into three distinct categories: portable GPS units that you can mount on your dash or windshield, aftermarket GPS units that replace the head unit in your dashboard, and factory units that are nicely integrated into your vehicle's dashboard.

For those that have older vehicles or dashboard designs that don't lend themselves to aftermarket units, the portable GPS unit makes a perfect choice. These units can be had for as low as about $70 and quickly escalate from there depending on what features you want (spoken street names, real-time traffic, Bluetooth capabilities, MP3 support, etc.). Another plus is that they are by design portable, so if you have more than one directionally challenged driver in your household, you can share the unit between vehicles.

The downside, however, is that you have unsightly cords running down your dash for power, and you have to remember to take the GPS down when your park your vehicle in public (lest you trust the unsavory individuals that would love the chance to “smash and grab” for a GPS unit or portable media player left out in the open).

Another option is the aftermarket in-dash “multimedia” GPS unit which also replaces the factory audio system in your vehicle. These units are quite the step up from portable GPS units and offer just about every feature that you could possibly want. In addition to the traditional CD/DVD, terrestrial radio, and satellite radio features, all of the usual GPS functionality that you would expect can be found with these systems.

When it comes to pricing, these systems are usually priced squarely between portable and factory GPS systems. They also require some basic knowledge of car electronics to install, but you can always call on a friend or have it installed by a professional.

The downside to these aftermarket systems, however, is that they don't always seem to “fit in” with the design aesthetic of the vehicle's interior. Your 1995 Honda Civic interior might just look a tad bit out of place with a 2010-era multimedia GPS unit in your dash. On the flip-side, some may find the futuristic looks of such a unit a fresh upgrade to an otherwise dowdy interior.

The final solution is the factory GPS system when purchasing a new car. For many people, this may be the best option because you get a GPS unit that was specifically designed for your vehicle and is neatly integrated into the dashboard. Factory GPS systems also often integrate multiple vehicle functions into the touch screen and can spread those controls to the steering wheel for quick access or to center console-mounted controls (think BMW's i-Drive or Audi's MMI).

The downside, however, is that factory GPS units can be extremely pricey and can often cost thousands of dollars. This is especially problematic for cost-conscious buyers that are simply looking for the GPS upgrade, but are forced to buy more expensive factory packages which might include GPS, leather seats, and a moonroof for example.

When it comes down to it, all often comes down to personal preference and your budget. Is portability a factor for you? Do you want to add a more integrated experience into an older vehicle? Or do you want a GPS system that perfectly integrates with your vehicle's interior design and control system? There's no right or wrong answer, but be sure to do your research before jumping in feet first.