This is not the best way to access your own computer. This is the best way for other users to access your computer on a view-only basis. If you want to access your own computer, use another linux/unix/bsd host and use the command "ssh -X". You will need to enable the remote terminal (ssh) service using the system>administration>services dialogue.

X over SSH is, as you should already know, encrypted. It also only allows much greater control over user rights, should you want other (less trustworthy, and believe me – everyone is less trustworthy than you with your computer) users to use the service you should use the useradd command and give them their own UNIX account which you can then set up to allow them to use what you want them to use and disallow everything else.

VNC is, by default, unencrypted and does not require a user account (and only optionally requires a password). It is a good idea to set a password, but we'll move on to why that isn't strictly necessary in a moment. The reason for its lack of security is because VNC is intended for use only on trusted networks – not over the internet. You should set up VNC without that third (UPnP) option, unless you want the entire world to have access to your computer. You can set a password, but you should rather avoid the port forwarding and simply tunnel VNC over a VPN should you want to connect from elsewhere. Since you are always connecting from a trusted host, it is ok not to set a password. However, should you be connected to (for example) a University network, it is advisable to set one anyway. That is if you are even ballsy enough to use VNC on a Uni network – it seems a bit silly to "trust" a network which is literally full of students (some of which, presumably, are studying computer science).

So, to sum up:
XoSSH (ssh -X) is for remote access.
VNC (vinagre) is for remote viewing.

On one final note, anybody who has actually compared the two technologies will agree on more than just a security standpoint – the remote control features of VNC leave a lot to be desired (as do the remote viewing features of XoSSH, for that matter, which is oddly how I came across this article – I was looking for information on setting up VNC to remotely view my computer from a laptop, because I'm lazy like that)