It matters a lot where you hike. Off-trail in some places means scrabbling through the brush or trying to navigate in dense forest with no landmarks, while in others it means strolling along a ridge above timberline with great views, nobody around, and easy navigation. I hate to go off-trail in a forest, love to do it above treeline. But let's say the going is good and the navigation easy, then for me the big differencve is in the level of detail. On a trail, I can look at the big picture becasue I don't have to pay attention to where my feet are going, while having to pay attention to where my feet are going when I'm off trail means I see a lot of little details of landscape that I tend to miss when I'm on trail. On a trail, I can think about something besides what I'm doing; sometimes that is good. Off the trail, I have to pay attention all the time to the micro-navigation, so my mind can't wander; sometimes that is good. When it comes to camping, off-trail is nearly always better since it means solitude and also surroundings that are closer to untouched. I get tired of doing one or the other exclusively, the best trips for me are a mix. I also do backcountry ski trips where, of course, it is all off trail since the trails are buried. I find that different from summer off-trail trips, because trails are not an option, which changes the way yuo look at the terrain.