There's actually tons of differences between the two. Plug.dj is international and provides an optional real-time chat translation feature. You can also play videos too, which is nice because you aren't just limited to audio only. You can make playlists and import music/video from SoundCloud and Youtube. Also, each avatar has its own dance and each room has DJ booth features. Oh ANDD when a room reaches a certain amount of users, you can unlock a strobe-light feature! Can't find any of this stuff anywhere else =) It's pretty awesome.

If you're looking for a site that has a great interface I'd try http://www.plug.dj/. They update the site very often and have a bunch of cool features that you probably won't find anywhere else. Playlists, song and video imports from SoundCloud and Youtube, unique avatars, room customization options, etc. It's also available internationally and provides real-time chat translation so you can interact with users from different countries without there being a huge language barrier.