Coverage does not come into it really, satellites are in the sky at a geostationary orbit of 24000 miles from earth, the only thing that would affect them is tall buildings, and huge mountains, If I have my data on, it gets a fix in seconds, in fact I have just walked outside, did a cold start, with data on, and it locked in about 20 seconds, and it uses very little data in order to do it, I had a Tom Tom 730 and it took the same length of time as my G300 to get a fix, after having used GPS on mobiles, I would never go back to a dedicated sat nav unit, in my job I drive over 60000 miles a year, and I can remember many many times, when my Tom Tom thought I was driving through fields, or down dual carriageways that did not exist.
I will take the mobile option every time
Coverage does sort of come in to it to a degree, and by that I mean line of sight to the satellites. The problem is that it refuses to give you a fix until it has it from 8 satellites, when just 4 would probably be enough. All those 8 satellites are not bang right over head. Hills, buildings, tree coverage can all affect it. Some cars roofs and even the antiglare coating on some car windscreens can reflect and block the signal. Where I am in the middle of a city surrounded by hills, with just the GPS enabled it takes a good 2 mins or more to get a fix. Which of course is the whole point of having the quick gps assist option.
I'm a delivery driver so a decent sat nav is an essential tool for me, I've used pretty much all the big brands extensively at some point and I'd agree the Co-Pilot does a better smoother more accurate job than the old Navman I currently prefer to use at work. I'll stick to the Navman though as work provides that one, and if someone is going to put my van window through to nick it, then I'd rather it be theirs than my phone. For personal use in my own car, then yeah its the mobile for me too. Dedicated sat navs just seem to be getting worse now, each new revision seems to get rid of some useful old features and pile in a bunch of new ones you didn't want and obfuscate everything behind half a dozen extra screens. One of the most useful features on the old Navman I use at work is the ability to select "Go to center of postcode". So if you're going to a named address or the street isn't listed, something like The Cottage, Main Road, Broadoak. 9 times out of 10 it will put you in the right place and I find it invaluable. We got some of the newer Navman's recently at work and that option has now been removed. Now you have
to select one of the streets it gives you as an option, but if you don't know the area you're going to, how are you supposed to know whether Main Road is nearer Penny Lane, Biggles Street or the B134whatever, and of course then because there is no number as it's a named address you have to select "Go to center of street". Whilst you will still end up some where in the vacinity, in the middle of a large housing estate or out in the sticks that can still lead to a lot of aimless driving around trying to find places. Not only that but the new Navman's have gone for a MS Metro look and you now have to go through twice as many screens as before to enter in your destination postcode. I thought the idea of bringing out new products was to improve upon the old ones, not make them worse.