(Ignoring Google and MS for a mo)
There are only 2 mapping providers - Teleatlas (now owned by TomTom) and Here (formally Navteq). Both are about equal in their accuracy, and number of streets with number etc, but for a given area, one might be better than the other.
All portable units, including phones, are shite. Always have been, always will be. Once you accept that, you can make an informed decision. My decision was to not use them when I chucked my last portable unit out of the window along the A38.
If using a phone based nav (which is doubly shite, as not only do you have all the issues of portable units, you have a small screen to deal with, poor quality audio to deal with, and invariably shitty mounting solutions), most options are free. So you can try Teleatlas maps (TomTom is free on iOS, and I think they might have released Android ones now), Here maps (Here app is free, although ad ridden). The online navigation options may or may not work for you - I vaguely recall you saying you struggled with signal in your area.
Most navigation algorithms pick a route, not necessarily the best route. Google Maps, for example, proper foooked us in Londonium last week, and we spent an hour on The Strand. Fortunately, the weather was hot, so there were things to admire.
So never an alternative to glancing at a map before setting out.