Do remember, however, that when recommending a portable unit, it needs charging and also needs to be taken out and put away and plugged in and unplugged!
Hey, come on. We've only had GPS for a few years now. Did you get lost a lot before GPS hit the scene? I can be "snapped and plugged in" in less that 30 seconds maybe only 15 seconds.
The major downside to a portable GPS is the delay in locking on from a cold start whereas the built-in units fire up immediately because they are always powered.
The major disadvantage to a built-in is that all the ones I've seen have "locks" that prevent selecting options while the car is moving because of safety features put there at the insistence of the company lawyers. And then there's the cost factor.
While you may disagree with it, Garmin allows you to disable these safety features which at least allow a passenger to select options instead of pulling over to the side of the road in order to have full selection capability.
If you're a techie, the built-in units will probably shine if you can figure them out. The one in our Prius comes with its own manual which is not the easiest thing to read. Also, certainly not user friendly unless you use it all the time. More than once, we had to pull over to the side of the road in order to enter a new address which it fails to take for some mysterious reason. A couple of times I've considered putting my boot into the screen.
The Nuvi is so simple it doesn't even come with a full manual. Instead, it comes with a 4 page quick start guide. Another big advantage for the portable is the ease of upgrading the map yearly. I realize it might be possible to revise a built-in with a new DVD, but I wonder how many automobile manufacturers even offer that service. On our previous Prius ('04), there was a safety recall that resulted in a new DVD, but no revisions have be offered on our '06 Prius to my knowledge.
I do understand the joy of the big screen built-in, but for me, I'm sticking with my portable nuvi 760 that I paid $399 for. Works great in my Eos, my Jeep Commander and any rental car we use and I can even use it for a hike if I wish.
So, I guess it just comes down to what you like.