Over the past ten years, I have been photographing nature and wildlife utilizing a 35mm format. Presently, I am interested in portrait photography but am overwhelmed by all of the medium format cameras available. I am drawn to the Mamiya 645 AFD due to its automated features and ability to add a digital back. However, I do not know whether there is a greater advantage to utilizing the larger formats such as 6 x 6, 6 x 7, 6 x 8, or 6 x 9 in portrait photography. I am aware everyone has their own opinion of which is the "best" system to use (i.e., Mamiya, Hasselblad, Bronica, etc.), I would just like to know if it would be more advantageous for me to go with a larger format than 6 x 6.45.