TomTom vs Garmin GPS Systems - GPS Car Tracking Devices

So I was wondering which TomTom or Garmin GPS System was better for my brand new car. I'm been interested in GPS Car Tracking Devices since they first came out a few years ago. Though I live in the States, I don't quite enjoy driving automatic cars and I'm always looking for japanese models. Also, I love getting interesting devices like GPS and music players.