I have this old MF 64 double disc plow, it has the (bent tube frame), it must have been one of the later models made.
my friend has a Ferguson double disc plow, it has a straight frame.
They work good, I use this one each year, will really roll the ground, but leaves it rough. Great plows when used for what they were designed, to break rough, rocky, root invested ground, before kick back plows.
They do pull easier than flat bottom plows. the key to good operation is the condition of the rear guide blade, it must be in good to excellent condition for the plow to track.