You might also want to take a look at some of the other features that may or may not come with gps nav units. More modern units have more features.
For now I'm addressing Magellan units as that's the brand of gps nav units I currently own.
I haven't ever owned any of the vehicle gps nav units in the past. I purchased new years ago a handheld unit, Magellan Meridian Gold that come with mapping software where one could create and download maps. One could create some very large areas such as state or multiple sate size. It worked well when hiking but I also used it to navigate in a vehicle while on and off-road
http://www.gpsinformation.net/mgoldreview/mag-gold.htm
My other equipment used for gps navigation is a rugged laptop with Delorme Topo installed. I found gps mapping running on a laptop is good while traveling longer distances and also when off-road in the forests and wildernesses. The laptop with a larger screen allows one to obtain a better perspective and overview of where ones going or needs to go. Currently I have Topo North America 10.0 installed which has topo and street maps (with elevation data, pois, trails, etc.) of the entire North America (lower 48, Canada & AK) and also Mexico. Map on screen can be displayed either 2D or 3D. It has lots of features such as routing, etc. Also there is USGS map database I added that has older USGS maps with information that's difficult to find on newer maps.
There are other good gps navigator brands out there all with pros and cons.
My current gps vehicle nav units:
Maestro 3100 3.5" LCD (older unit, works ok for basic navigation, can create and store addresses and pois, which are limited)
Roadmate 2036T-LM 4.3" LCD (another older unit that comes with lifefime map updates)
Maestro 4700 4.7" LCD (older, not a recent unit 4.7" screen, has voice recognition and bluetooth for pairing with a cell phone, etc.)
Lifetime map updates can be beneficial if you need to keep the road map and pois more recent.
Looking at some of the older Magellan Maestro and Roadmate series gps units. There's some differences between Maestro and Roadmates such as different features.
This article goes into some differences between the two.
http://www.differencebetween.info/difference-between-maestro-and-roadmate
"Both the devices use the Nokia’s Navteq navigational maps"
"The most common difference between the two is that Maestro is believed to be a better option for off-road settings, while RoadMate is more suited for road navigation."
_____ Voice recognition _____
Some of the Maestro and Roadmates are able to accept voice commands, when voice recognition is enabled there usually is a limited number of voice commands (at least with older models) The Maestro 4700 includes several basic voice commands.
Home, Where Am I?, Nearest Restaurant, Nearest Restaurant by <type>, Display Map, Done, Main Menu, Help, etc. The above commands will have variations such as instead of "Where Am I?" will accept - "Display location", "Display current location", "I’m lost" and "Current position"
Some reviews of the Maestro 4700 showed it was weak in voice recognition and could use some improvements. However I think perhaps because it's an older model you may need to speak into to it in a certain way.
Voice recognition is continual improving, newer units may have some of the bugs worked outs and more commands. A good voice recognition device allows for a device to learn a particular user's voice. I'm not certain about whether or what gps nav units have voice learning capabilities unless it's built-in and learns a particular voice without the user being aware.
Magellan website usually has a pdf file with a list of voice recognition commands their units with voice recognition.
_________ cell phone pairing capabilities __________
Another thing that may come in handy is to be able to pair with your cell phone via bluetooth. Some phones have better compatibility and capabilities when paired with devices than others.
With bluetooth pairing capabilities you can pair you cell phone to answer and receive calls. Some models this is done from phone menu on the the touch screen. I'm uncertain but assume later gps navigation units may have voice recognition phone control commands.
Pairing your cell phone with the gps unit allows for hands free operation. If your gps nav unit includes voice commands for a paired cell phone this would be even better.
The Maestro 4700 when paired with a cell phone has phone menus from a pop-up screens to e.g. receive a call, to end a call, to redial, dial a number from it's address book or poi, import contacts, call home, manual dialing, speed dialing, Answer a call and enter numbers for automated services, mute, adjust volume & microphone gain.
Perhaps newer nav units have more cell phone pairing features which also depends on the pairing capabilities of a cell phone.
Using a cell phone while driving differs between states and jurisdictions.
e.g.
California,
Connecticut,
Delaware,
Hawaii,
Illinois,
Maryland,
Nevada,
New Hampshire,
New Jersey,
New Mexico,
New York,
Oregon,
Vermont,
Washington,
West Virginia (plus
Washington, D.C., Puerto Rico, Guam and the U.S. Virgin Islands) prohibit all drivers from using hand-held cell phones while driving.
If you cell phone is paired wireless to another device you then don't have the cell phone in your hand which is the primary purpose of these use of cell phone in a vehicle laws that vary from state to state. Safety laws keep changing, the last I looked via google some states there is no hand-held ban but there is a ban when texting.
