You know, I hear this argument for Ngons quite often lately.  It's almost reached the point where it has become the "anti" modeler's mantra, so to speak: "If it renders ok, then it is OK".  I'm in the midst of my second year of advanced modeling courses at a University, and this has been hotly debated in our classes before.  Your arguments have been brought up in similar fashion, and there are opposing views to most of it.  I'm just going to point out some flaws in this logic, and leave it at that.

"When it comes to static, flat (planar) surfaces, Ngons are perfectly fine to use, and sometimes strategically intelligent!"

"By definition, triangles are planar, so it makes perfect sense to incorporate them into planar surfaces, and could possibly save you some rendertime in larger scenes, as your engine doesn't have to break down the quads or ngons into triangles.   Using quads for flat, planar surface space on models is just awaste* of resources, and time.*"

You do realize with these two statements, you have completely contradicted yourself, and defeated your own argument for Ngons being used for planar surfaces over quads.  Let's think about this:

In Geometry, I think we could all agree that a triangle is the perfect plane shape.  No matter where you move it's 3 points, a triangle will always form a planar surface.  Yes, triangles are simple to raytrace, and are pretty much identified the same way across any 3D software package.  That said, stepping up to FOUR points in a shape does complicate things a little bit; by a factor of two, as it takes two triangles to create a quad, as you yourself have said, and would be correct.  However, the flaw in your logic comes when you suggest that NGONS are somehow more efficient to use on planar surfaces than quads.  There is no math which suggests that a planar surface, which consists of FIVE or MORE points, is more efficient and simple to calculate than 4 points.

While it's true that quads are more complex, and can present many more problems to a render engine than a triangle, Ngons present an almost unlimited number of potential  problems, and are certainly far more inefficient than quads.  While that extra point on a quad can lead to non-planar, unpredictable polygon behavior, NGONS have all the same issues, multiplied!  Plus, with a quad, you can define the triangulation (provided your modeling application allows), where with NGONS, the triangulation of the polygon at render time is left to chance.

Ngons as intelligent modeling strategy?  No.  Sometimes faster than figuring out quadrangulated surfaces?  Of course, but it's bad practice and way more inefficient to leave them in a model.

I've run into very few cases where I couldn't figure out how to get rid of all the triangles in my models.  I think I may have two or three freebies up right now, out of 21 total models, that have something like 2% triangles in the topology.  So it's NOT impossible to get all quads, nearly all the time.

If someone wanted to use my models in a game engine, it's very simple mathematically to decimate a quad mesh into tris.  There's tons of ways to automate that procedure, and end up with a good triangulated model.  However, if I had a model full of tris, and someone wanted to make it all quads, for whatever reason, they would be in for a whole lot more work, and quad automation isn't very predictable or clean.  So I model everything in quads.  Hard surface, or organic.  It's more versatile, and "intelligent" modeling in my opinion.

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