MP3 and BT may not be important, but what about being able to load and save routes, waypoints, etc. ? Garmin often omits useful features in lower priced models. I'm not saying the Nuvi models you chose are like this, but some Nuvi models definitely don't have these things.
My point is to go through the comparison lists item by item before you settle on a model. //
They can do that. But the Zumo comes with the CD: the Nuvi does not.
Simple comparison. The 500 has topo and road maps of the lower 48 states. The 550 has road maps of the 48 states and Canada.
I have a 500 as well as a Zumo. If it had a headphone jack and MP3 player it would trump the Zumo because of the topo maps and form factor. If listening to directions isn't important to you, it's an excellent all-around choice: I've used mine hiking, boating and biking as well.
I bought the Garmin motorcycle mount for it on Amazon.
To put it in perspective, I used my Zumo for two years before I ever hooked up the earphones. I know plenty of people who listen to an iPod and just use the GPS for visual reference. I think it's a pretty good choice and has a number of advantages towards the used StreetPilot 2nnn units folks are buying.
What we need is a hack to add a headphone jack from the speaker output....
How much of a GPS whore am I? At work or home we have the eTrex Legend, Summit, Nuvi 205, 260, 360, 500, 660, 765T, and Zumo. We sold off the 2610, 2720, and 2820.