SS= Speckled Sussex? Hmmm. I never thought of my son's SS as "smart." She worked her way to the top of the pecking order quickly, so she's not dumb (a slight bully to other hens perhaps). Most of our flock are Orpingtons, so it's easy to look like a genius next to them. LOL
The kids have fun training our birds & the Dom is the easiest to work with. She's so curious, outgoing, and willing to please. The SS is fearless and will fly up into the kids' fort and even seems to enjoy going on the swings & slides with them. The SS is a lot of fun, but the Dom is our problem-solver and has a longer attention span. With only 2 to compare, I'm guessing I see more indiv personalities than breed specific traits.
I have so many birds, I think I see the stand outs. As a breed, the SS are the friendliest. I know this could very well be just the ones I have decided to breed back over the years having that trait. The SS are by far the most out going.
While the DOM's are not unfriendly, they are not the first to approach me or want to be held. The boys are down right stand offish.
The legbars are flighty as a whole, but there are a few of them that are very curious. The Partridge Chanticler roosters are more friendly than the hens.
But it as a whole they are average. I find a few either way in all the flocks.