I own the Garmin C550, IMHO...the menu's are very intuative, the directions are spot on, when you miss a turn, the recalculations are very fast, the FM traffic receiver (if available in your area) works very well, it alerts you of accidents and high volume traffic ahead of you and will/can re-route you around the problem. i plugged it in when i got it this past xmas, and the unit was ready to direct. Garmin gets my vote, they have consistant map and firmware updates on their site as well, just plug in the usb cable and hit a webupdate shortcut after you install the software. The size of the unit is very good and does not obstruct your vision. the bluetooth feature works well with my Moto razor V3 (you can call from the gps if your phone has this feature). it also allows you to look up and get directions to; resturants, atm's, banks, and more in the area you are traveling, as well as call the places, all through the gps unit. Also the anit-glare coating on the screen works very well.
I haven't used the TOMTOM, but on cnet, one of the complaints is the mount is prone to breaking and is of poor design.
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