I've got an older Garmin Rhino, with an OnX chip (for MN). I love it. I've had Garmins (tho not this one) in the Mule, Dragoon, and Huachuca mountains in AZ, and the BWCA in MN, and all sorts of places in between. Any GPS will struggle with especially thick canopy or canyon walls which impede its view of the sky.
In a previous position I used ArcMap and played around with moving waypoints and related data between Garmin, Google Earth, and ArcMap, synthesizing data from different sources. I found it easy enough but I was pretty used to the software.
I hate using my phone as a GPS. Once that battery drains, it's done until I'm back at my truck. My Garmin takes AA batteries and I can keep it going all week with what's in my pack.