It could be either. Search results can vary from browser to browser, depending on what you’ve searched for before, whether you’re logged in to Google, etc. You should always clear your cache and log out of any Google/Bing accounts to get a truer picture. (Although results do, by their very nature, vary.)
Google now takes mobile-friendliness into account when returning results from mobile search, so that could account for differences between mobile and desktop results.