It can indeed be compared. They both utilise computational capacity in an algorithmically distributed fashion as a means to an end. The former requires specialised single purpose hardware, is a profligate waste of resources and mindshare for no sound economic, technological or environmental reason -- whereas the latter piggybacks in the cycle gaps on spare commercial and domestic computing to analyse radio telescope data with the goal of perhaps some day finding genuinely world changing evidence that intelligent alien life is out there in our light cone.