Don, I don't know about the advantages/disadvantages other than maybe two wheels just carrying a heavier load and maybe preventing it from tilting and scalping in some areas. It seems to me that most frequently you see the one wheel on 3-point hitch shredders and the two wheels on the pull behind, and of course the pull behind from the drawbar would need two to keep it level. However, I had a neighbor with a very old 7' 3-point shredder that had two wheels. The wheels and their height adjustable brackets were mounted onto a square tubular length of steel across the back so the entire wheel assemblies could be moved to change the spacing between them. Then one of his boys hung one wheel on a stump and tore it up, and instead of replacing it, he just moved the other wheel to the center and made a one-wheel model out of it.
