Can't comment specifically on either, have been around Renn and Farmking in the past, IMO of the two, Renn was the better. Myself I got some huge older one that was built in Ontario called a Fastcut. Can't recall exactly how large diameter the rolls are, but they are all of 16" or more and it is about 30 inches plus wide. And has smooth rolls...and no not that they are wore down, they were smooth from new. Just from how it is built pretty sure it originated in a feedmill and is of industrial intent, and while I can't compare it to others and I have never really cared enough to test it for max cap, with those large smooth rolls running at about 700RPM(which is fast by industry standards in feet per minute, but where it runs smooth) she packs it away, more so with oats than barley, and moisture effects both. IMO simply based on physics, the larger the rollers, the better a mill will feed under most circumstances. Also things like moisture, kernel size, and more have huge effect, so I would take any claimed capacity with a grain of salt.
I have seen that offset idea in those rollers, and really IMO you still have the same contact area between them as with ones that are on the same plane horizontally, but do they turn at the same speed or does one turn faster?...I seem to recall someone made one that was set up to drive like that, idea was you got some tearing action as well as the crush of the rolls.
Not sure about anyone else but I'm sure there is, locally Barrhead Machine is very well respected for remanufacturing or regrooving rollers, even when broke thru they can fix them for less than a new machine.