I actually toured with a Garmin Edge Touring, and tried switching to a phone app (Komoot) for 3 days recently.
I used an android phone only for navigating, it had no data on it, and did offline navigation. Used Wifi / Wifi shared by my phone for uploading stuff and updating routes.
- As far as navigation go, the phone just kills the Garmin. It shows a map you can actually read, and clicking any zoom button doesn't send the device lagging for dozens of seconds/minutes (to show a map you don't see much more).
- I also loved the ability to modify along the way or plan at night at camping. With the Garmin, I would have needed a computer. Now I can plan on my phone and sync it to the navigation app. Though, newer garmins do have komoot sync.
- Battery life is more than adequate, with screen always a Motorola G5 lasts about 6 hours. My Edge Touring might have lasted 8-9 hours, but with a suitable battery pack, the phone is suitable.
- The bad: In bright sunlight, the phone screen won't be very readable. If you use a rain cover, it will be even worse and the tactile screen won't work properly. You need a proper mount, stuffing the phone in an ortlieb map holder you get unusable visibility in sunlight and horrible touch functionnality. Sweat drops falling on the screen click on your behalf. GPS chips on phones just don't work nearly as well as dedicated units. I have an Etrex 30 that is way superior to my Edge Touring which is way way superior to my phone.
So I am myself very puzzled, hesitating between a newer GPS with komoot sync (I will NEVER EVER use Garmin Bascamp since I tried Komoot), or rocking the phone.