I definitely like the Garmin design a little better and Garmin scores very well in all the reviews I read, I do own a gramin GPS which I use for hiking.
For the car, The TomTom features were more appealing to me, mostly because of the bluetooth integration. However I was very close to getting the Garmin. Also Garmin does not offer their software for the Mac, with TomTom I can bypass the PC and upgrade maps and POI with my phone.

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04 X5 4.4