I have buff orpingtons, EEs, barred rocks, and I used to have Rhode Island Reds.
But -- by far -- the best egg producers I have ever had are the two Production Reds that I bought from an organic dairy farmer/egg producer out in rural West Tennessee.
These eggs have a strong, chocolate brown shell, and even though the two birds are only about eight months old right now, their eggs are already bigger than any and all other hens I have. My buff orpingtons, barred rocks, and EEs are a year and a half old -- which means they are producing bigger eggs now than ever -- and yet these little Production Reds eggs are both larger AND higher quality than the best of my other hens.
And the best thing of all -- the little Production Reds are the friendliest little hens you'd ever meet. They are just little darlings, and adapt well to confinement.
I'm thinking in the future I'm only going to get just two kinds of hens -- Production Reds and blue egg laying Ameraucanas or EE hens.