vnc vs nx

http://www.wikivs.com/wiki/NX_vs_VNC

NX allows users to create new X11 sessions and forwards all X communication to the remote client.VNC simply forwards what a logged in user sees on the desktop similar to how video would be transmitted.

（１）Platforms
Because NX is based on X, it only works on servers where X is present, namely, *nix operating systems (including Mac OSX with X11.app). NX does not run as a server on Windows but can run as a client on Windows.VNC works on all servers because it simply images the desktop and sends it as pictures instead of X11 calls.

（２）Performance
　NX performs faster than VNC because it works at a higher level, requiring less data to be transmitted. VNC communicates through compressed bitmap screenshot updates of the desktop while NX communicates through compressed X11 calls. For low bandwidth connections - such as some internet connections, mobile broadband, etc. - NX can display in real time in cases where VNC is too slow to be a feasible option.
　While this is true for remote, low bandwidth connections, VNC is quite a bit faster in a local area network. NX has considerably more computational overhead.

（３）Multiple clients
Because NX logs into the server as a session, multiple clients would each get their own session.VNC support multiple clients in the same session only which is very useful for training purposes.

（４）Audio
VNC does not support audio; NX does.

（５）Security
VNC is not a secured protocol (although it could be tunnelled) , while NX may use SSH natively in order to establish a connection