Beard hair is wirey, chest hair is fairly good, but curly. Body hair will largely remain the same on top of your head as it was when it was in its original location. There is one difference, body hair can grow longer when relocated to the scalp. That has been my experience. Arm hair worked well for me because they are nice fine, straight hairs that gave me added density.
If you use finasteride and your body hair seems to be the same, that is you have not lost any noticeable amount, I would not hesitate to use finasteride after a bht.