I currently use the following Sat Navs
Blaupunkt DX-V in my VW Sharan
VDO MS-5500 in my Beach Buggy
Becker BE-6100 in my Ferrari
Garmin Quest II on my Honda Deauville
Blaupunkt is the most awkward as far as user interfaces, but the most reliable and accurate for actually getting you there.
The VDO is just plain awfull, and we have stopped selling them - its only because we couldn`t give the last one away that it ended up in my Buggy.
The Becker is OK, but as only a basic pictogram and voice, its difficult to compare to the colour maps of the others.
The Garmin on the Bike is OK, and the easiest to input data, but I wouldn`t trust that the roads it send me down around this part of the country would be suitable to drive down in a car.
I`m always interested to hear feedback on other systems, as we have been selling these now since they were first introduced around 12 years ago, and remember fondly the Alpine that only covered within the M25 and sold for a tad over 8 grand !!