That's only half right , lighter but faster firing so better at suppressive fire, was a key part of why the British stuck with the 25pdr rather than follow the trend of increasing calibre like other nations. In other words they most definitely did want a lighter calibre SPG, not until the 60's with its replacement, the Abbot, did they go to 105mm.) the Priest was replaced by the Sexton largely because it used a nonstandard gun and ammunition, not because there was a preference for lighter self propelled guns.