Quote Originally Posted by 127
The most rational argument I've seen for 6x7 is that a lot of pro's are shooting for magazines and stock libraries (which ultimatly end up in magazines and the like). In these cases the rectangular format (ideally 6x9 but 6x7 is more practical) allows more of the negative to be used in the final image. 6x6 would need to be cropped to fit a magazine page.

Many magazine editors like the square neg as they can crop it any way they want, giving more options for final page layout. No doubt there are editors who prefer the rectangular formats, but I doubt either would turn away a good photo.
Just because you have a 6x6, doesn't mean you can't have a 6x7, or 6x4.5, or 4x5 or 8x20 or...