Not just check the spec, not just check the home screen (Samsung copies Apple UI anyway), try something hard to get it right. Like try to pinch-zoom the map in its map application, try to scroll/zoom a complicate website (like wenxuecity.com ;) ) in its browser.
Also try some hot applications, like facebook/twitter/tumblr clients on both platform, see what is the difference.
I think Android (including Samsung Galaxy S3) still lags behind iOS (iPhone/iPad).