I have three horses on a small property. We use a ground-driven Frontier (John Deere) MS1105G manure spreader. Its the largest ground-driven one that was available.
When spreading I usually wish it was bigger (allowing fewer trips), but when storing it for the winter I usually wish it was smaller. I think that means we sized it about right.
The floor is poly-coated. The walls are galvanized. The rest of it is painted. Its been stored about 50/50 in barn & outside for about two years now and so far no signs of rust. I grease it up before using and apply oil to the chains.
It has some pretty aggressive teeth on the beaters and shreds the manure pretty well. So far it has served us very well. Can't complain.
John Deere Ag - Frontier Equipment Features for Manure Spreaders - 175 Bushels or Less