Solar Thermal Gains in HB / EnergyPlus - discrepancy between polygonclipping and pixelcounting methods

@chris making reference to our past conversation on radiation analysis, many of the LBT users probably realise how solar radiation analyses - per se - are very useful when relative figures are considered but risk becoming pointless when the linkage to solar thermal gains is not clear.
So even the availability of multiple ways to calculate solar radiation externally risks become a vanity project unless this is linked clearly to the calculation methods and results that can be obtained by means of thermal / energy modelling. I may be wrong in this, and I immensely appreciate the work you guys have been doing, so please let me know if there is something I am missing here.