The best way to determine the effect of an automation like RSAs is to test them with a Campaign Experiment, a feature available in both Google and Microsoft ad platforms.
Please visit Search Engine Land for the full article.
Original source: http://feeds.searchengineland.com/~r/searchengineland/~3/abfc2d3AJKY/will-rsas-help-or-hurt-your-account-this-script-will-help-you-figure-it-out-330199