I only own the Rolleicord III equipped with a triotar lens (triplet design) from f8 down there is no real difference to my Rolleiflex of the same Vintage meaning prewar uncoated. The V is post war and coated the xenar is a tessar clone and has more contrast than the pre war triotar. If your main objective is to photograph buildings I'd say get another camera than either the III or V. The corner sharpness of both the triotar and V is not the best in the camera world, on the other hand if you mainly want to do portraits photos with the occasional Building and landscape get the III. The Triotar lens is best used as a portrait lens but it has a certain magic with landscapes kinda like the leica glow. BTW the III has a build in eyeleverreflex finder.

Dominik