High level observation:
Most free mapping apps don't allow you to cache the map. I have a selection of assorted map apps to allow me to cache enough foreign climes to get me from A to B as each will only allow a relatively small chunk of the planet to be stored on the phone.
I have a hilarious 10" satnav if I want - an old Dell D600 running Autoroute 2003 using a GPS dongle / Garmin 12 (the Serial connector has screws to stop it falling out!
) to tell it where it is. Needless to say it has it's limitations, but the maps came with the software. I could do the same with Landranger if I had noticed Memory Map's "Whole of Britain in OS 1:50K 2D / no extras" for £40" deal a couple of years ago
Free apps are fine in cities & places you have lots of WIFI & / or 3G+ phone signal to grab the maps in real time.
Try Google maps in the depths of Glensomethingorother where a signal is in utopian fantasy land- Phrases involving chocolate teapots come to mind!
A sizeable chunk of the cost of a satnav is the maps.