Orpingtons are fairly laid back, lay well, and sometimes go broody. they do well in cold climates and are dual purpose so the hens will still have meat if you decide to butcher.
Leghorns are flighty birds, they lay excellent, lay a large egg, and are non-setters. They are better suited for warmer climates and are great confined or free range as their flighty nature makes them less prone to predator attacks.
the Delaware is very similar to the Orpington in that it is a dual purpose breed. They are noted for their excellent meat although I have never tried it so cannot give you a personal endorsement. They also lay well.
Delaware & Orpingtons lay brown eggs. Leghorns lay white.