The 23-year-old actress locked lips with Ryan in 'Crazy, Stupid, Love' last year and also plays the love interest of her real-life boyfriend Andrew in upcoming movie 'The Amazing Spider-Man' but refused to reveal who she preferred kissing.
When asked by chat show host Ellen DeGeneres, who was a better kisser, she replied: "Apples and oranges, you know."
Although Ellen pressed on by asking "So is that an apple or an orange?" Emma responded diplomatically, adding, "I love all fruit."
Emma also starred with Ryan in upcoming movie 'The Gangster Squad' and the pair are both being considered for the lead roles Christian and Anastasia in the movie adaptation of erotic novel 'Fifty Shades of Grey'.
Meanwhile, Emma was terrified when Ellen played a prank by bringing out a fake spider to scare the arachnophobic star.
When Ellen took out what appeared to be a real spider, placing it on Emma's lap, the actress was horrified, exclaiming: "I'm going to throw up."
When she discovered it was fake, she said: "You are the worst. Why would you do that to somebody?"
Ellen replied: "Now when you see a spider, you will think it's like that [fake]."