If they use similar input to regular feed, they should have similar output. Except it's just the meat and no bones, brains, or other animal parts that modern humans find largely inedible. However, most companies started out by using animal products as the nutrient solution (e.g. some kind of fetal serum for beef products) which meant killing animals nonetheless. Multiple companies say they have solved the issue but at the same time go around saying "proprietary! proprietary!", so we don't really know whether it's just smoke and mirrors for their investors.