When the shafts in the machine run crossways, that puts the bearings on the outside, where they're easier to work on. When the shafts run lengthwise, it's not so easy.

If you run a drive belt fast, and slow it with gears at the last step, the belt has less torque to transmit and will last longer. If you slow it with a gear-box as the first step, you will have considearble more problems with it.

If you have a 3 foot wide feederhouse and present the crop mat from that to the front of a 20 inch rotor, you need to either twist or fold that crop mat to get it into the business end. A thin mat of the proper dimension to get into the cylinder with no fold or twist is just naturally easier on things.