I have quite a collection of both. I love paper and keep a road atlas in my pickup. That said I use several apps on my phone: Advenza Maps, Maprika, Trailforks, Singletracks and MTB Project. I have 95 maps alone in my Advenza Maps app. I tend to ride solo on new trails while making lengthy road trips, so I like arm myself with all the info available. My paper map collection isn’t as extensive, but I have several and just recently bought one for the Bozeman, Montana area.
I have been able to navigate unknown trails mostly using a combination of smartphone apps. During long rides, I put my phone in airplane mode, which makes the battery last a very long time. I often use MotionX GPS for my iPhone, which allows me to download OpenStreetMaps terrain maps and overlay GPX files sourced from multiple websites.
Lately, I have been able to do something similar with my Garmin Fenix as I learned to upload the GPX track to the watch, albeit without background map.