Subjectivity Along the Buddhist Path

I noticed that when I meditate on breathing, which I've done about as long as the four immeasurables, I tend to nevertheless hear sounds such as a television or sounds outside my house. When I meditate on the four immeasurables, I don't hear the sounds in the environment. I'm not distracted at all unless I get quite tired. And is it possible that for me personally, metta provides more concentration? I'm especially curious of this **subjectivity** aspect in Buddhism. Given the focus on empirical evidence promoted by the Buddha, **how does one know / deal with aspects of the path that may be different because of one's own mental disposition?** More specifically, *how* would I ascertain if perhaps some aspects of the path are more difficult to me personally, and whether another way of proceeding would be more beneficial? How do I know what is essential, and what is peripheral?