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.