Medium Format
When I used film, I always owned a medium format system in addition to 35mm and large format cameras, which served as my second-line system for images that couldn’t practically be made with the large format. This changed in 2003, when I replaced my Mamiya RB system and 35mm cameras with a digital SLR camera.
Medium Format - Advantages
Medium format, with a larger image size than 35mm camera, is the a good compromise between the image quality of larger formats, and the portability of 35mm. While I preferred to work view cameras as much as possible when I photographed on film, there were many situations where a view camera was just not sensible, or where there wasn’t time to reload the larger camera’s film.
Medium Format - Personal Camera History
Over the seventeen years I worked with film, I owned numerous medium format cameras; a Mamiya 645 (1988-90), a Yashica 124MAT (1989-91), a Mamiya C330 (1990-93) and a Mamiya RB 67 (2002-2003). I have also worked with Hasselblad, Bronica, Pentax 67, and Mamiya RZ cameras.
Between 1997 and 1999 I used a 6x12 Cambo roll back on my 4"x5” camera, which gave me 6 images to a roll of 120 film. 
I really liked this aspect ratio, as it permitted me to crop slightly and produce truly “panoramic” images, or leave the image as a 1:2 ratio and have a strong horizontal or vertical image. It was very convenient to simply carry the roll-film back in my camera bag for when I needed a panoramic image.
From 2002-2003, for a year I had a near perfect system comprising of a Mamiya RB 67, which makes 10 exposures on a roll of 120, using interchangeable lenses. System consisted of 127mm and 50mm lenses, two backs (so I could shoot two kinds of film simultaneously) and a prism finder. It was a fabulous camera to use, though I constantly had the frustration of wishing it was a view-camera.
The last medium format camera I owned was a Fuji GSW 6x9. The camera is a rangefinder (rather like a Leica on steroids) which is a very different way for me to work, but the framing on the camera is very accurate, and its operation is very comfortable. Having a fixed lens would seem to be a negative factor, but it does have positive aspects. It gives me only one lens to learn, and limits the expense of the new system. I pretty much only use this camera outdoors, primarily for colour work, thereby dedicating each of my cameras to a different media (35mm to infrared, medium format for colour and Konica 750 infrared, and 4"x5” for traditional B&W).
My medium format film of preference was, for black and white, Agfa 100, and for colour, Agfa XPS 160, which has a wonderful colour pallet.