X11 forwarding is not even the best option for remote rendering on X11. You will get better results with VNC or NX/Xpra.
For me, X11 forwarding:
- works out of the box, no config needed
- works on an application level rather than desktops; this is key
- doesn't require anything network-wise but SSH
- doesn't require me to modify servers in tightly controlled environments
These are all mandatory requirements for me.