Comment RDP uses the Windows display model (Score 1) 179
RDP's display model is, basically, GDI's; in fact the RDP layer appears to Windows as a display device driver exposing all the usual APIs. Which means that the client can push pixmaps across the link, get a handle to the opaque pixmap object (an HBITMAP in Windows parlance if I remember right), and then issue a draw call that just says "draw this pixmap" (or part of this pixmap).
For a lot of samey-looking GUI applications where elements like button backgrounds and borders are reused, this can add up to a huge savings in network traffic.
Of course, X can do this too; in fact the XRENDER extension can do Porter-Duff compositing of server-side pixmaps with an alpha channel. But if you compare RDP making full use of the Windows display model with X11 where the app developer coded it like a VGA video game and just scribbled into a frame buffer which it pushes to X for display on every update, then you're bound to think "holy shit, RDP is fast" and "holy shit, X is slow".