The Pentax is said to be a good and sturdy camera with good lenses. I do not have personal experience with it though. It is often recommended to get the version with mirror lock up, but since you want to shoot portraits this would be of no use I think. The 105/2,4 is a lens capable of amazing results from what I´ve seen. Otherwise, Mamiya RB67 or RZ67 with 110mm and 180mm lenses are the classic portrait machines for 6x7. These are very modular also. Do you need the cameras to be portable? These are rather big. If you need a sleek and light camera I would rather recommend a Rolleiflex TLR or Hasselblad. I assume that you want to print on conventional paper sizes? If so, and because you wanted the maximum of information, I would recommend 6x7 over 6x6, since the latter is not more than 6x4,5 or 6x5 when cropped to meet standard paper sizes.