So, which cradle is best for you? GPS accuracy and speakerphone performance is about the same, so you can't go wrong with either. It really comes down to a question of form factor.
Anyone who wants to leave the cradle with the car, and use it with multiple iPhones and iPods with different cases, will appreciate the flexibility of the Magellan's mount. However, people who want to carry a slim cradle with them from vehicle to vehicle will like the svelte TomTom.