I like using AllTrails for navigation (w/ topo and compass as backup), and mostly for review, but most of the people using that app are hikers, not backpackers. It's difficult to find feedback on AllTrails that helps with picking a good trail while getting reviews about incorrect signage, good/bad camping spots, water sources, etc. Is there a better app to use for backpackers?
I agree with the analog folks, maps and compass. When I get to go, I'm generally out for relatively long periods of time, and need to ration phone battery energy for essentials like contacting my wife before she alerts the rangers! I am taking notes here for good apps to peruse trails prior to hiking, though. A good topic, thanks!
Gaia premium. I like being it because I can map out routes and waypoints on my laptop, print out a copy, and it matches exactly what's on my phone.
My boyfriend used to use Gaia and I, a topo and compass. Then he got a new phone. Gaia and his phone don't get along. Its apparently a known problem. On his phone, Gaia throws stray points way off the trail so it looks like you've hike 2-3 times as far as you actually have and on trail that doesn't exist. I believe there is a list of incompatible phones on the Gaia website. He used Green Tracks now I believe.
But something good you can do with Gaia, and maybe the others, is that once you have everything loaded and ready to go, you don't need an internet connection or high accuracy GPS connection. So you can put everything into battery saving mode, turn off all the transmitters except the lowest level of location/GPS service to really extend your battery life.
I've never had any issues with it. I can put my phone in airplane mode and just use Gaia, then turn airplane mode off and send a few texts each night, take a dozen or so pictures a day, and the battery will last 6-7 days. I'm happy with it.