Because I have been wrestling with what kind of camera to use for my current project, I have also been confronted with the issue of the square vs. the rectangular format. This is not a new phenomenon for me. Back when I was in grad school, I had a lot of trouble trying to find my voice as an artist. At the time, I used 35mm, 6x7, and 4x5 cameras, but never was comfortable with any of them. It wasn't until my father gave me an old panoramic camera that had belonged to my great-grandfather that I began understanding that format can make a huge difference in the kind of work you do. This camera, an Al-Vista Model 5D, took 5" roll film and took a picture with roughly 160˚ angle of view. (I used this camera with cut-down 11" x 14" sheet film exclusively for the Shadowing the Gene Pool series.) From the start, I discovered that the long, slender panoramic format gave me a creative voice that had been missing. There was something about how I could arrange things in space that completely spoke to me, and since that time I have used a variety of panoramic cameras and loved them all. The fact that panoramic images are rectangular isn't lost on me, but I don't seem to be limited by them creatively in the same way that I am by less-long rectangles.
I didn't start using square format cameras until much later, but discovered when I did that they, too, allow me to work with space in a way that allows me to speak with my pictures in a way that the conventional rectangular formats (35mm, 6x7, 4x5) never have. As a beginner, I never realized the powerful impact that an image's shape and dimensions can have on the meaning of a photograph. Now that I do, I choose my tools for any given project with great care.