I have used Backcountry Navigator on my phone for past seven years I think, love it, last year I bought a Garmin Oregon to give it a try, man talk about a battery hog, couldn't tell when it was actually shut off or just in sleep mode, sent it back right away! To each their own, but I don't think you're going to save on battery weight etc with a stand alone GPS, also I will have a phone and a charger pack regardless, doubles as a camera and the possibility of getting a signal and being able to communicate with home is priceless! I download topo, Forest service and satellite imagery at home on the WiFi and I have way more map options that way than with a GPS.
I'll caveat the above with this though, I primarily use mine in the mountains, if I was wanting to find a place to hunt on private land, the onx might be a better choice, but I'd still have it on my phone!