Things I like about X:

I can have applications running on all sorts of different hardware sharing a single desktop, and that desktop can have whatever style and whatever complexity or simplicity I choose.

Things I like about VNC:

If I lose a connection to a machine, accidently or on purpose, I can reconnect and nothing is lost.

But the models are very, very different, so you need to actually use both, perhaps at the same time, to get an idea of what each can do for you.