So many people say leghorns are flighty, nervous, and bullies. I often wonder how many of those people have actually owned leghorns or have been around some quality stock. I find them very active birds, but other than that not much different than other breeds. In fact, in the egg coop the leghorns get picked on from the new hampshires and seem about equal with the easter eggers.
You don't go into their pen flailing your arms around and they are just fine. Curious and smart (for a chicken) that lay lots of eggs on little feed.
In all honesty you'll get lots of opinions, and Henderson's chart isn't much more than his experiences and opinions. Different lines of the same breed are going to be different and nothing is guaranteed.
For a fantastic egg layer that's pretty mellow, the red and black sexlinks are hard to beat.
I have had different experiences with sex links. I have tried several times to get "nice" ones. Every one of them I have had have been horrible bullies in my mixed flock.
I wonder if they would still be awful if they were in a flock of just sex links......