/3/ - 3DCG

I want to make low poly modular buildings, which could be used in building a town. I want all buildings to share one texture map.
I would like to know what is a good ratio of triangles to pixels. As in if I have for example a wall that could be build of 3 units wide and one unit high, should I have the mesh be split into 3 quads with each sharing a 1 to 1 texture space, or have one quad that is 1x3 and have that part of texture 1x3 as well.
Basically is it better to have 1 quad with 32 by 96 pixels, or 3 quads with 32 by 32 pixels. Obviously it would be scaled up a lot, if I am not clear in my description, let me know and I will do my best to clarify

Pic not mine