I have never used a barley crusher but I am sure it is great from what I have read here. However, when I was ordering mine I knew I was going to motorize it so I wanted a 1/2" drive shaft. You don't need it to motorize it, but it is nice and cuts a step out. Monster Mills was offering a free 1/2" drive shaft upgrade when I ordered mine, so that was nice.
So if you plan to hand crank get the barley crusher since it comes with a handle, if you are gonna motorize, look for something with a 1/2" shaft.