I'm not even going to ask for benchmark proof to see how VNC could possibly be faster
I work for RealVNC and we've commissioned several internal reports for competitor product comparisons, VNC came out on top in most areas, I can try and get you the specifics if you want but it's pretty boring, i'm not going to lie. The problem is that most people are using the legacy version of VNC based on the VNC3 protocol, which is outdated.. other than that people use VNC Free Edition, which although updated to the VNC4 protocol (4.1.2 being the latest FE release) is still an outdated piece of software, it's got several issues, isn't compatible with Vista and depending on bandwith/latency can run like a dog if not configured correctly.
VNC PE/EE on the other hand are in constant active development and have been updated with a multitude of features/fixes/patches.
You can tell i'm giving you the spiel because I work for the company, although I do actually agree/believe it, otherwise I wouldn't be spouting it on a public forum
The only argument against it as far as I can see is the obvious one, that you need to pay for it; which is a very valid point, I wouldn't use it myself if I didn't get it for free ^^
When you 'initiate' a remote desktop connection, it 'creates' a virtual session, you cannot connect to your actual 'Deskop' screen, i.e. screen:0, known as the console session.
VNC on the other hand connects to the console session by default (logmein does this aswell), you're literally viewing the computer as it is, not creating a new virtual session.
This has its good points and bad points. If you actually *want* to create virtual sessions, then VNC isn't for you (not under the Windows platform at least, under Unix you can control the console session aswell as creating multiple VNC sessions)
