My absolute favorite hen ever, has been my Crested Cream Legbar, Melody! She has laid very well, large-XL light blue eggs and has the sweetest, predator-wary & independent nature. They are not dual purpose, with smaller frames. I have many breeds that get along very well. The Barred Plymouth Rock & my Splash Easter Egger are nearly as sweet and both very well behave, but Easter Eggers can vary in temperament somewhat. Brahmas & Australorps are also very sweet.
Neat historical fact about the CCL is that they were created in England by none other than Dr. Reginald Crundall Punnett FRS, British geneticist/zoologist (of the squares!) I never imagined I would adore one of his creations in my 60's back when taking HS biology in 1980. They are available inexpensively in a light, cream-breasted crele (invisibly barred in hens/obvious barring in roos) feathering like Melody, or more expensively in solid/non-barred white or much more expensively in a barred Opal. None yet recognized in US APA! Often available at feed stores or mail order. Single comb, so not best for very cold climates.
The (barred) purebred CCL chicks are naturally sex-linked so can be separated easily at hatch, but either (cream/opal) barred variety, can also be used to create sex-linked hybrids when the hen is bred to a solid main body feathered dark roo. Only their sons will have a white spot on their dark downy heads.