And to continue where JS left off.

All games render in real time so all models should be triangulated prior to importing into an engine. Triangulation works 100% when models are all quads.

The issue is all about rendering, also its worth noting if you are going to convert your polys into Sub-D or NURBS then n-sided polys will give a lot of issues as will 3 sided. So keep 3 sided to a minimum (only use where there is no other option) and never have n-sided polys.