Well Sid I don't think that that's such a fair argument since he's using Milkshape, which only supports tri's.
But yes, I think that in general for anything organic or something that will deform you should definitely model with all, or most, quads, since not only is it good practice but obviously helps deforming the model.
If you're modeling something that isn't going to deform, like a gun, the need for quads gets less needed, since it really isn't going to matter too much, but as Sid said, I think that you should model that way anyways since really, it's a good way to model, it makes the edge flow "look" a lot better, and is very good practice for the modeler him/herself.
And besides, it always depends on what you're using the model itself for, I mean, if you're for example using FPSC it should really be fine to keep the sort of edge flow that BVG has right now, since it works for him and makes it possible for animation, while in other engines or whatever you're putting it in there might be a higher demand on good edge flow than anywhere else.
Also if you plan to work as a 3D designer you're most likely going to work under somebody who'll give you assignments, which will probably require certain things, like for example if your boss asks you to make a fairly "Next-gen" weapon with 3000-6000 polygons he'll most likely want it to be in most quads.
There is one good thing about having only triangles though, that being that there is really quite difficult to get non planar faces and alike with triangles, while with quads it's really easy.
One of the big issues with modeling in something like Milkshape, that only supports tri's, is that it's very hard to maintain a good topology since it's very easy to just go crazy with T-Faces and such, which is why Milkshape is really more meant as an easy, cheap animator than anything else.
Alucard94, the member of the future of the past.