My dozen geese do a great job with maintaining an already-short yard and (when somewhat confined) trampling down tall dry grasses in the off season. They aren't nearly as effective with shrubby brushy stuff. For example, this year I got behind schedule on pasture management due to illness and accidentally grew half an acre of horseweed (erigeron canadensis) as tall as my head -- the geese can help knock that over and thin it out, but they won't eat it. Also don't make much of a dent in the blackberries, etc.
But I suspect that geese/sheep or geese/goats would be one heck of a tag team.
And re: noise, my geese are loud, but not as loud as my female ducks. I usually don't find them obnoxious. I've been surprised by how much I enjoy having a gaggle around. I have a dozen geese, mostly pilgrims.
