GPS Why not a smart phone?

I am traveling all over SE New Mexico oilfield roads some of which are so new, they are not on any map. I have google earth pro, and some of the roads may show up visually but are not in the google database. Some of thee roads have no data coverage so I end up using both phone and Garmin. When I get to a location, it is easy to save in the Garmin for future reference. AND the Garmin leaves bread crumbs and that route is there until I delete it. This is huge for me when I am on a road that is not on the map. The company gave me an Iphone. Imaps is the worst nav software ever and is not used by me. Not intuitive at all. The Garmin gives me speed limits which is handy since the company monitors my speed. For general use I still sometimes use both and often get different results for routes and ETA. The phone seems to be more accurate on ETA. The in-dash GPS in my personal truck and Garmin in work truck often lead me to businesses that are out of business or have moved. The phone does that less often. Even though I've been on a route a hundred times, I still program it into something because I like to know the ETA.