Read reviews before buying a GPS for business travel - Consumer Reports, Amazon and other sites.
Consumer Reports is not a free service but their online subscription site offers well-researched GPS model chart comparisons. Amazon's reader-reviewed posts are a random grab bag of rants/raves, but can be a worthy place to get a general sense of popular opinion. GPS Review is an excellent source. There are many other detailed GPS review web sites worth looking into.
Look for sites rating specific model pros and cons: read about hardware, screen views, navigating, POI, route planning, re-routing, voice quality and extra features. Business Travel says: decide what you really need in a GPS and read many reviews before you buy!
A few quick comments on the Big Three makers of portable GPS devices:
1. Garmin - When asked about easy navigation, the Nuvi line is considered tops by the Bellevue, Washington Best Buy sales team. Staff also reported less returns on Garmins overall as compared to Magellan and Tom Tom units.
Garmin Nuvi devices also have the largest POI databases in the industry (six million pre-loaded points of interest).
Note - this entire line is pricey. If you have the budget, buy Garmin's Nuvi 660 or 360 for the best array of usable features and ease of use.
2. Magellan - Maestro - Commonly considered next best after the Garmin lines, this is the business traveler's best bet for great features and ease of use at a more economical price point.
Got AAA? The Maestro 4000 and 4040 also points out Triple A approved vendors, where business travelers can flash their AAA card to get good discounts on hotels, motels, car parts, auto repair shops and misc retailers like Lenscrafters. For non-AAA members, the Magellan 4000 POI directory is a let-down; it's not as comprehensive as Garmin's database (the new 4040 is a big improvement with 4.5 million entries).
The navigation is not nearly as intuitive as the Garmin Nuvi series either, although Business Travel found the learning curve on the Magellan Maestro 4040 pretty easy after a few test drives.
3. Tom Tom - Since the Tom Tom doesn't call out specific street names, the otherwise top of the line Tom Tom One trails a distant third after the better newest Garmin and Magellan units. In several freeway practice drives with Tom Tom One, Business Travel found it's waaay too easy to miss the correct turn or exit in multiple turn instances. "Turn LEFT in 200 feet" just isn't as helpful as "Turn LEFT on Market Street." Even the Multiple Point Routing doesn't make up for that lack. Enough said.
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