I think the main argument for remote X is that it is so easy to use between 2 true X11 environments. You just `ssh -X` to your target and start running programs.

On Windows or OSX though... If you were going to install X11 why not skip it and just install VNC?

Maybe I don't want to run a full X session on my remote machine, just to run a simple X client and have it displayed on my local desktop?

VNC is no alternative for running individual applications remotely. Remote desktop != remote X.

True, for one app, ssh -X is usually better

Still, most of the time, running only one application is not the usage model. Or it's a simple thing that doesn't need X, just ssh

Remote desktop allows remoting only single applications, though. That's how stuff like the XP mode with Virtual PC on Windows 7 works.

That's exactly what 'ssh -X' is for.

(But tastes much better as 'ssh -XC')