Tomtom
For what it's worth I've had a Tomtom Rider for a few years now, it's proved to be an excellent piece of kit. Mine is the V1 but they've bought out the V2 now.
As I understand the Tomtom has free updates, Garmins have to be paid for.
Plus there is also a thing called mapshare - a lovely system which allows you to update the database with changes to roundabouts, traffic lights, no entries etc.. then when several people have confirmed the same changes your maps are updated in your sat nav.
You pays your money.. bl4hbl4h