There is a noticeable difference between the sound of open and closed headphones. But it is nothing at all like the difference between stereo and surround sound. They are both stereo. It's easier for open headphones to create the impression of a wide soundstage, but that doesn't mean closed headphones can only have a narrow soundstage, or that open is better - it depends on the headphone. The main difference is that open more readily lets in the sound from your environment, and closed tends to isolate external sounds. When comparing cheap headphones, it's easier for open designs to sound better, but with even moderately expensive headphones closed designs start sounding really good.