The only possible downside to used reloading equipment is if the prior owner did not have everything properly adjusted, particularly the rotating shell advance. Too much play can cause accelerated wear. I wouldn't hesitate to buy used Dillon equipment if everything appears tight. I've owned an RCBS Rockchucker since they first came out and that baby has proven indestructable.

All the manufacturers pretty much use the same manufacturing techniques in that the frames are cast. Therefore, they probably use the same raw materials.