I have two sets of shoes that I wear while hiking. My favorite by far are my light weight trail running shoes. I have worn them on 9 mile hikes without any break-in, and went blister free. From a comfort perspective they are simply amazing.
I also have a much more expensive hiking boot, which is made of durable leather, however every single time I wear them, even for a couple miles, I get blisters. I cannot seem to break them in to the point where they are comfortable to wear. When is it worth going through the pain to break in leather boots versus just sticking with the much more comfortable and light weight trail running shoes? I typically just day hike so my pack weight is often less than 20 lbs.