X2There is a best all-around chicken breed based on my criteria. I know a little about chickens.We are having a discussion here for information for people and for fun.
Some of the breeds you mentioned have been mentioned by others in this thread.
Dominique is an excellent all-around chicken breed. The first American chicken breed, Pilgrim Fowl. They may be a little on the small side. If they were a little bigger, they would probably win for all-around chicken breed based on my criteria.
The Sussex is another very good breed. The Speckled Sussex is the most common. From what I could find, I think they would probably lay less than 200 eggs a year. I know different strains will have different characteristics. That is why a strain can be very important also.
I think the Australorp could be a contender for best all-around chicken breed. It lays well, is heavy enough to be a good meat bird, forages well, is hardy in heat or cold, and goes broody sometimes.
That is a good point you made when discussing Leghorns. A person probably only needs to have a couple of broody hens to do the work of raising chicks. A person might be able to breed Leghorns up in size some to have a very good all-around chicken, but that would take a long time.
For a large mediterranean breed that lays lots of huge eggs and very good forging and heat hardiness, consider Minorca.