It’s most likely an issue with the smooth groups or your normal map, or both. Are you baking from a high poly mode? What program are you baking in? What 3d modeling app are you using?
This thread talks about it a bit http://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts/p1
It’s still a good idea to avoid super thin tris, but quads vs tris really isn’t the issue here.