Metal Bender Question

Hello list.

I am working on the design of a universal metal bender and would like
the input from the group.

Benders are classified into three types

<ram bender> works like a log splitter and used in muffler shops
it's fast but it does require hydraulics and it does crimp the work and
leave tool marks.

<rotary draw tube benders> works by clamping the work to the side of the
die and the die is rotated and a follower roller forms the metal around
the die as it is being turned.
Supposed to be the best method and is used on CNC machines

<unknown> Where the die is fixed in the center of the bender and the
work is held next to the die by means of a pin and then a follower
roller die is used to form the work onto the die held in the center of
the machine. J&L Industrial sell a hand bender like this for small
work, however I want to make a large version that is more adaptable to
other operations.

MY question What is the advantage of the unknown and the rotary draw
type bender? Seems to me that since you are forming the metal around the
die by means of rotating the die or rolling the stock around a
stationary die the result should be equal. We all realize that any of
the three methods shown here will work but what makes one better then
the next?
I am only interested in manual hand operated benders at the moment.

There are several types of benders out there.
Diacro is a good one and then there is Hossfield and then the import
copy of the hossfield. With the exception of the fact that the hossfield
and the copy of the hossfield will bend a larger diameter of a given
stock size. Is there any other advantage of one VS the other?

Does the hossfield bender have any advantages over the diacro bender?
Is there another bender that is better in certain respects to the diacro
or hossfield bender and if so why?

If you where looking for a bender what would me the max circle dia that
you would want to bend material. What would be the max stock you would
like to bend (keeping in mind this is a hand bender).

Thanks for your input.
Regards
Stan