IMHO, it's the crowd it's serving that differs more than anything else.
If you are remote connecting from multiple locations and multiple OS's, I'd probably find that VNC would be easier (though SSH clients exist on most (all?) OS's too...).
I'm pretty sure I've read that VNC is less secure, and poor performing than alternatives.
VNC offers the ability to have multiple windows with the same user. Something like virtual desktops, but without the switching. So, you could setup one "environment" and have 25 people VNC in and all have the same environment without having everyone's windows on their desktop (where I believe with SSH it's a remote view of the actual desktop).
X11VNC server is included as a module in the latest xorg, so it may feel easier to use for a first time user.
I feel vnc to be more sluggish, but that could just be me