It depends on a few things in MY case Chrissy:
1. I can't read maps
2. If I'm driving solo and on my own, I just programme the sat nav and off I go. When I used to work around the country from the North to the South West, I had to rely on AA or RAC print outs and that's really stressful.
However, when towing, I wouldn't dream of relying on the sat nav. As I do the towing and Phil is in the passenger seat, I rely on him and as you say, use the sat nav as a back up.
If you go out and about by yourself in the car, then in my opinion, it's priceless.
In reply to your original question, I think the general opinion is:
1. Tom Tom market leader
2. Followed by Garmin
That's only what I've heard from other people so can't comment for the accuracy of my post. I will say one thing though, I went away with my bro the other week and he's got Road Angel - I didn't reckon much to it at all.
And, by the way, you're talking to a woman who CAN get lost with sat nav..............
Lisa