Not sure, there's probably some people tracking that, if you're getting more returns you might want to ask yourself how those are possible though (more often than not it's just blatant front-running of votes on already popular authors to get max returns and may not have the best effects on the platform and your investment). Having said that there's a new hardfork planned that'll make curation rewards linear soon and pretty much everyone will earn the same returns from curation so it won't matter much who you delegate to.