I can only add my experience with our hand cranked WonderMill Jr. I really like the mill, but of course it takes a long time to get enough flour to make a loaf or preferably two. While I have a son and husband to help me grind it, we all rejoiced when my husband added a motor, toothed gears and a chain. It doesn't grind it fast, and the flour stays pretty cool. The flour has always come out nice and fine, but when done by hand, we would usually run it through twice. With the motorization, it takes one grind and it's super fine and lovely for my breads. Granted, we have the handle that could be easily replaced on the machine if the power was not on, but I think for long term purposes my husband would figure out a bike cranking method.
I'm very happy with my purchase. I spent less than $200 and I am very happy with the mill. Hope this helps!