Garmin is a sponsor of our show so I know there product pretty well. Although it depends on what you want to do with it. I like the Garmin nuvi for the car nav stuff, but If I go backpacking, I am taking the Magellan handheld, the triton series is good.
For hiking Magellan is just better. They use the National Geo maps for the base maps and for hiking they are great.
As for the car stuff, most in car navs have a similar base map, most just use different color representation and icons. The main differences are the routing systems they are using. I would rate Garmin, Tom Tom close to the top for small removables, the better bargin will be the Tom Tom, but if you can afford it the Nuvi is the way to go.