Hi; I thought I would add my 2 cents worth in.
You didn't mention what types of subjects you are shooting. If you are doing wedding/event photography I would lean towards the 645. Landscape or fine art, especially with B&W or color transparencies I would lean towards the 67. The difference is more pronounced between 35mm/6x7 then 35mm/6x4.5. Very rough math has a 35mm neg at 864 sq. mm, 6x4.5 at 2700 sq. mm., and 6x7 at 4200 sq. mm. If you do a lot of medium to long telephoto work it is easier to find and afford teles in 645 vs. 6x7. The equivalent of a 100mm portrait lens in 35mm is a 150mm in 6x4.5 and 200 in 6x7. The point that you can crop more is valid but you loose the advantages of the larger neg. I owned a Pentax 645 (mf) with 55, 75, and 150mm lenses, which I bought to shoot weddings, but for personal use I also tended to use that instead of 35mm. If I still had it I would only need a 300mm lens and maybe a 1.4 TC to complete a very useable kit for me. I have wanted a Pentax 6x7 for years, but I see that as less of a replacement for 35mm for me (and, unfortunately, not in my budget in the near future) I no longer shoot wedding and would like the extra neg size. BUTCH "Each man had only one genuine vocation - to find the way to himself" Hermann Hesse (Demian)
