I think that factory farming is more sustainable agriculture, because I think that they are more efficient. A sustainable farm might be nice to the environment on paper, but they also do not do anything to fight diseases on the plants and animals. Factor farms have mainstreamed the process and work more efficiently.
I think its just a better practice to consider agriculture, factory farming just seems very off to me. I know that people don't like these types of practices and to they just seem unethical. I know in time maybe these practices will be pushed out of the way, and new ones will be put in place.
Sustainable agriculture is the way to go in this life. If you do factory farming the conditions are usually horrible and full of diseases and the poor animals are cooped up and not being treated correctly and they are usually eating foods that are full of antibiotics which then you are eating and then when you get sick, you go to the doctor and you have to try a bunch of antibiotics because your body built up a resistance from factory farming.
I do not believe it is fair to compare these two practices, they actually deal with different things and are used in tandem in some circumstances. Factory farming has more to do with livestock. It is interested in intensive animal farming. Sustainable agriculture can be used when referring to livestock, but it actually has more to do with farming the ground and growing crops. You can't replace one with the other, they are not interchangeable.