In reply to Choss Weasel: I have an iphone4 with memory map, but like others said it is ok in good conditions , i.e. when it s warm enough that the battery does not fail, or you don't need gloves, which makes using a smartphone tricky. In good weather of course ,your map and compass, mostly make the phone redundant.
I much prefer my Mapping Garmin's with ( again with MM, ) and memory cards that I can swap out various maps on, the batteries are long life ,and they are easy to swap in really cold weather. it s ' waterproof' rugged, and the signal is usually pretty good across the country.
The biggest issue I have with my phone is reception, sometimes my O2 reception is good, but it really varies to poor to nothing. I have taken to carrying a cheapPAYG on a different network, to give me better chance of getting reception if I need Phone call.
Lots of advice on here, none from me, I'm just stating what I use and why.
You will have your own ideas, and I'm sure you will find something that suits you.