I think you are mostly right that RDP handles vector graphics, while vnc is mainly screen image based.
Another difference is RDP informs clients when changes occur, while VNC server waits for clients to request the screen updates. This also makes RDP more efficient.
However, as users want more and more of the same experience as the remote computer, RDP nowadays seldom send vector graphics, i.e., RDP pretty much also send screen image diffs. The reason RDP is still faster is because Microsoft has built-in drivers inside Windows to detect display changes while VNC uses workaround to do that, you can imagine Microsoft does much better job in this. So even both protocols send the same image, Microsoft is much more efficient. As a matter of fact, no Windows remoting software is as efficient as RDP (I know Citrix's ICA, let's put it under same RDP category).
If you plan to remotely use Chrome for videos, you mway feel disappointed by RDP, as it's slow unless you turn on RemoteFX, but it's only available from Windows 2008 servers (I am not sure if Windows 8 supports it, though).
So my suggestion, use RDP whenever possible.