With your question, you might refer to both physical properties and soil nutrients. Then the answer gets strictly correlated with the management of the thinned material. Assuming that the branches are left on site, their presence allows to retain more water at ground level and to better control soil temperature and moisture. In some specific cases, the retention of branches can also reduce erosive processes that might occur. Regarding nutrients, the decay of the material helps to replenish the soil reservoir of micro-nutrients, but also nitrogen and carbon. Of course, if branch material is collected from the site, these effects might not happen.