The larger the format the longer the lens for the same given perspective. So if you have a longer lens for a larger 6x7 format, you have shallower DOF. A "normal" lens for a 35mm piece of film is 50mm while for 6x7 format piece of film requires a 90mm lens roughly. You will lose DOF with a 6x7, not gain.
Thanks. so are you saying that a 6x7 lens of 100mm f4 would be equivalent to a 35mm lens of 50mm f2, but the 6x7 lens wold still provide less DOF ?