For most backcountry navigation I use a topo map and compass when necessary. Generally I'm following known trails and combined with some basic awareness of cardinal direction and land features I don't really need electronics.
This fall, I'm going to a large desert that's fairly off the beaten track with little in the way of established trails. There are some features I'd like to be dead-accurate on (water sources, primarily) so that when I find them I'll be able to accurately record their position for future use.
I'm trying to decide between my phone, a Samsung Galaxy S5, or a dedicated GPS receiver (Garmin, etc). GPS receivers seem a bit more bullet proof, seem to have a more stable operating system, and as a dedicated device probably have better battery life.
What would be the main reasons why someone would pick one versus the other?
Also, I have a 16K mAh Anker battery, but given the weight (~11oz) I'd prefer to not lug it around if possible.