Marc Batters , Jun 15, 2011; 02:27 p.m.
Rob, Another factor driving your decision is lenses. For 6X17cm, you only need lenses that cover 5X7." You will need lenses that cover 8X10" for the 4X10." Cost wise, either choice is sort of a wash, as the 4X10" may cost less upfront, the film holders are not cheap and lenses can cost a bit more for 8X10" coverage.
If you want a faster handling camera, then you basically will have a camera with little or no movements. If you don't require a fast handling camera, cost wise, I would go with any conventional bellows camera of your choice, with movements, and get a reducing back for panoramas, sheet or roll film.
I basically am doing the latter, but on a smaller scale. I have a Cambo 4X5" and a 6X9cm roll film back. For 6X12cm, I actually cut 4X5" negatives down to 2 1/4" to fit my film scanner. This set-up allows me the versatility to shoot full size 4X5" film when I want, but also allows for composing and shooting panoramas when I want, and I have movements galore to shoot narrow verticals, (think Space Needle or Eiffel Tower).
Ultimately, you are the only one that can decide which path will work best for you. I don't require handling speed, so my approach with the Cambo is working well for me. I don't know if I helped you any, but those are some of my experiences on the subject.