Years ago there were all kinds of breeds of cattle, pigs, chickens, etc. As farming became more specialized, the breeds were reduced in number, and the surviving breeds were changed through selective breeding to fill a very particularized niche - egg production, milk production, weight gain, etc. The selective breeding of domestic turkeys has yielded animals with high quantities of desirable breast meat (let the snickers begin) but left them incapable of natural reproduction. Lard was in great demand decades ago and the pigs were breed for high fat content. People now want leaner meat and the pork industry has brought leaner hogs.
The Holstein cow can produce all kinds of milk (as well as manure). They also need all kinds of food. The Hereford and Angus steer has great weight gain and high quality flesh, but requires lots of high quality feed to do it.
For homesteading/small farm circumstances, some of the older/heritage breeds are more economical. It is easy to produce milk and meat when the grain and high quality feed is being pushed to the animals. But, how will they fare on grass and hay?
Jerseys and Guernseys are small cows, eat less, and produce less milk. However, on a basis of input to output, they do well. There are Dexters, Milking Shorthorns, etc. These, and other dairy breeds, are not used in commercial dairies.
There was a disease outbreak several years ago in the Caribbean Islands. US pork producers wanted the foreign pig herds eliminated to prevent the spread of disease. The industry offered to replace the hogs with US factory farm hogs. Problem was, the US hogs needed a higher quality of diet and housing than what the people had.
Up through about WWI, the US diet was largely grains, fruits, and vegetables. Coming into WWII, new machinery, seeds, fertilizer, etc. yielded too much grain for human consumption. So, we started feeding it to animals and moved to a meat based diet.
In the homesteading/small farm situation, you want the animals to eat whatever the humans can't. For instance, in India cattle eat the inedible grasses and produce milk. The cattle take plant matter that is not usable by humans and make milk/butter that is.
So far as utilizing the nutritional value of food most efficiently, humans consuming crops directly is more efficient. Animals eating crops and humans eating animals is inefficient. However, the "mini" breeds may be less inefficient than the usual commercial breeds.