A good outcome of the NPPF is that it does remove the ambiguity over this issue (see previous posts). It places the emphasis fully on the process of assessment of significance and this will then lead the decision makers and professionals to follow one or other assessment - whether it generates "substantial harm" or "less than substantial harm", based on its significance.
Another interesting question that will need to be explored in case law is what is "public benefit". This is not as straightforward as it might seem as it doesn't necessarily mean public use. Housing does not generate a public use but the consequences of development of a derelict or brownfield site, a gapsite or a building which has been torched or which has many environmental health problems could have significant public benefit of different degrees.