To be fair if we knew the answer then there would not be a thread with 300+ responses on.
My take is that both sweetspot and POL training can and will work. However I think there is less scientific support that POL works, especially evidence that is specific to cycling. @mcneese.chad started a thread where he was going to try a POL period and see how it went. I followed the whole thread and to be honest I don’t think I every saw a final definitive summary but I get the view that it was as the Scottish legal system says ‘Not Proven’. It may or may not work but hard to call.