You probably can't beat the hatcheries on the leghorns for efficiency and egg size. The hatcheries would be getting the commercial hatching stock, not show type, so would be small bodied big eggs.
Smaller people probably focus more on the breed, and will go for conformation before egg size and feed efficiency. Unless of course the small breeder had commercial birds. I have had leghorns from hatcheries and they all lay jumbo eggs by the second year, and at least large the first year.
You might have to wait a year for the egg size to reach maximum from the leghorn laying stocks. They all start out "small" but get bigger over about 4 months or so.