Strava for cycling over MMR in my opinion. It’s more cycling-centric and brings data to rides and a nice level of stalking built in (who else was on the trail when I was there, how did I do compared to my friends/rivals, etc.) And the platform is more straightforward with less adds and “fluffiness” compared to MMR and it seems to sync with everything pretty well. I use MMR to create routes still on my computer and I’ll upload some of my GPS files to it, but Strava is my go to for my stats compilation.
I got started using Strava as a tool to find trails. There are plenty of apps for that today, but years ago there were not. When I was traveling to a new area I would search for strava segments in that area. I could easily differentiate mtb from road segments by looking for loops and/or zig zaggy red lines. At the time I had no interest in the data it captures. I just wanted to ride and had no interest in following others or seeing my lap times. As the Strava app improved I got more interested in it. The ability to add photos of my activity was a nice improvement. Now I use it not only for recording my rides, but also keep track of trail work. I save the workday as a workout and add photos to remind me what was done.
Tried Endmoto and Map My Ride, none of them were very easy or accurate to use for me. Strava has been mostly flawless, and I LOVE the heatmap, it help you find trails in a specific area that are unlisted.
Trailforks is more for finding and navigating existing trails. It works best for finding your way around a trail you are not familiar with. It is a database of trail maps. Strava is a database of your past rides. Think of Trailforks as your map and Strava as your breadcrumb trail. Both apps are good for their intended purpose.
I use Trailforks, All Trails, and MTB Project for trail navigation. None of the three have all the trails so I use the one that has the trail loaded that I am riding that day. On trails new to me, I run one simultaneously with Strava so I don’t accidently turn on a horse or hiking trail. I find MTB Project to be the most user friendly. But when it doesn’t have the trail map I want to ride I look for it on the other two apps.