Paradox wrote:When modeling, it doesn't make a difference which is used as everything becomes triangles when exported.
It is worth keeping in mind, though, that you have little control over which direction the quads are split, so at some point (either during the last stages of modelling or before you even begin, depending on how much of a control maniac you are

), you may have to consider the matter and whether it affects your particular model.
Case in point: If you do that merging (at their centre) between two connected corners (vertices), as mentioned in the classroom thread, you may get a convex surface on one side and a concave one on the other. I tested splitting the quads of these and wound up with both sides convex. Now, what if I had wanted cavities, rather than bulges? -It is necessary to think of these things, if your quad is too "bent". (..and easy to handle; flipping the edge between two triangles is just a CTRL-F away.)
I talk too much...