+3 on the Garmin.
I bought LOML one a few years ago and she liked it. Then she saw a deal on a Tom Tom with more features, so she bought it. After a few days of trying it, she returned the Tom Tom, since the Garmin was easier for her to use and understand.
Don brings up a valid point about the cost to update maps. If you live in an area with a lot of new developments like he does, that can be a big consideration. On the other hand, if you're in a more established area, it's not much of an issue.
My Lexus has a built-in nav system, and all of its data is stored on a DVD that's buried somewhere in the back of the car. It's a 2001 vehicle, so the data it's using is at least 10 years old. (The cost of updating the DVD is more than a new Garmin with all the bells and whistles would cost me, so I'm not going to update it.) Anyway, even with an outdated database, I'd say my Lexus knows where it's going about 99% of the time. If I lived in one of the newer suburbs of LA, that percentage would surely drop. I have Google maps on my iPhone, plus a couple of navigation-specific apps, but the display is too small to use while driving. I only use it to find the places my Lexus doesn't know about.
Whatever system you end up with, I think you'll wonder how you got along without it.