I think that if you're comparing something like a Linhof 612 or Fotoman or something like that or even a 6x12cm Noblex to a wooden 5x7" camera or custom 5x10" or the more common (as far as esoteric formats go) 5x12", it's the film holders that are going to make the biggest difference in size/weight of the kit. Other advantages of dedicated 6x12cm cameras are that they are handholdable, so you can use them for different kinds of photographs, and 6x12cm negs fit in a 4x5" enlarger. Of course, bigger neg has obvious advantages, depending on the means of enlargement that are available to you.
Another question you might consider is when it might make more sense to shoot 5x7" cropped to panoramic, rather than stitching two 5x7" images made with shift. If you're just stitching two images, it's not so difficult, but if the light is changing rapidly, the subtle difference between two shots you're attempting to stitch can be maddening.