If you have multiple video cards and you want to use one for your Dom0 aka host and the others for your VM, “PCI Passthrough” is the path to take because it is way easier to setup. In conclusion this is what I will try first because I have my HD7950 and the i7 integrated Intel 2000.
On the other hand if you just have one video card (e.g. in a laptop) you have to deal with a little patching and kernel compiling to get your video card to the client. Maybe I will try this later on even though I do not need to.