VNC is dog-slow compared to RDP. RDP is slow compared to xpra. What xpra does is sending a h.264 video stream (some other compression algos are also available). Also, xpra can forward the whole desktop as well as single applications. Far preferable to any kind of RDP server.
However, the xpra client is somewhat strange and inconsistent when it comes to CLI/UI behaviour.
RDP will also send a video stream depending on what's happening on screen. It'll try to detect the appropriate transfer mechanism as chunked screen updates increase and decrease in frequency, assuming both sides support the necessary protocol versions.
Video streams can be a real issue if you're working over a slow connection, especially when your application is using small text. RDP will handle remote GUIs much better, as low bitrates tend to make text unreadable.
Of course RDP also supports streaming individual applications.
Personally, I think RDP is undefeated at what it was designed for: controlling desktop GUI applications. On Linux, that's not the case, though, and xpra will provide a very good alternative.
However, I find very few good xpra clients outside of Linux distros. For example, when I look for xpra in Google Play, the first three options are Microsoft's RDP client, two X11 servers, and RealVNC. F-Droid lists nothing at all. I suppose u could try the HTML5 client but it's kind of a bummer. The situation seems to be the exact inverse of RDP: very good Linux server, difficult to use Windows clients on all other platforms.
However, the xpra client is somewhat strange and inconsistent when it comes to CLI/UI behaviour.