Sinner, the topic of your thread poses the question, "Ngons and tris: Sloppy modeling or intelligent strategy"?  The proposed conservation of immeasurable nanoseconds of computation at render time does not answer that definitively, and it doesn't prove that ngons are more efficient for any reason, even in regard to planes. I simply can't help but think, when hearing all the excuses about when and where to use ngons, that it's all just smoke and mirrors; an excuse to just slap a quick fix where there is a problem, and not be bothered to properly correct it.

When I render a cylinder that is capped with quads vs. one that is capped with ngons, the render time is exactly the same, down to a tenth of a second.  That's as much as is recorded in my render log window, and I believe that's as much as I ever need to know.  I don't need to know if I'm saving nanoseconds in my renders, because it will never ever make an impact on anything. Clearly, even if I did multiply my quad cylinder X 1000 in the scene, the render time vs. the same number of ngon-capped cylinders isn't going to change drastically; not enough to be advantageous in any way.

On the other hand, keeping ngons in my models, even on planar surfaces, could certainly result in undesireable issues later on.  That much is irrefutable.  Ngons ruin good topology; they're very difficult to map properly, they introduce pinching and creasing issues if subdivided, and they make selections and editing of objects difficult.

Ngons are not dealt with the same way across 3d platforms.  3dsmax pretty much introduced the ngon to 3d modeling workflow, so I'm not surprised it handles it very efficiently internally.  That's not to say other applications will have the same result, and it definitely doesn't mean it's worth using them in the finished topology of your models.

Leaving ngons in a model just doesn't result in good modeling strategy, and I don't believe that's just an opinion.  You are compromising the integrity of the object, for what? A few seconds of prep time? A nanosecond of compilation time to your render engine? 

The CheckMate 3D Modeling Standard suggests always fixing ngons, and I personally will never intentionally leave them in any of my models.  There is always a mathematical solution to fixing ngons, and I highly recommend anyone modeling any surface, hard or organic, fix them before calling it a complete model.

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