greencastle_ducks,
I'm pretty new to chickens but I've had a couple of Buckeyes for two years, and have between 5 and 10 each Buckeye's, Speckled Sussex and Australorps from a July hatch this year. They are all from hatcheries.
I'm from northern Illinois, we just had 8" of snow followed by temps down to -1F, so I can help you with cold hardy. If you don't count frozen combs I believe all three are about equal in cold hardiness. So far none have ventured out into the snow but they all seem comfortable with the temps. My coop is not heated, this past week the young speckled Sussex roos have little frostbitten comb tips, and the parts of the wattles that touch the water when they drink look like they might have a spot or two also. The Australorp pullets have larger combs and wattles so I imagine as the winter progresses they might also have some frostbite. The buckeyes of course have no trouble with combs or wattles and the cold. Last year my Faverolles roos lost the very end tips of their single combs.
The speckled Sussex are the friendliest. When I give them scratch as treats the Sussex are always the ones on my lap. None mind being petted while they are eating, a couple of them will choose to sit on my lap even after the food is gone. They talk to me while I'm getting their food ready. I ended up with three roos. Two are indifferent to attention, the other one used to be my friendliest chick, then testosterone kicked in and he is too busy to sit with me, but he is still friendly and very good with the girls.
The Australorps are next on the friendliness scale. They seem to go through fazes when they are wanting to get petted, then not really interested. One today came up after all the food was gone and snuggled up for a long time. One of them has never been interested in being petted. I don't have any Australorp roos.
The Buckeyes are also wonderful. I only have one pullet that is interested in being on my lap but they are all under my feet when I walk into the coop. They seem very intelligent and are interested in all that goes on but also have this no nonsense air about them. I've been trying to work with the roo a bit more. I want to make sure he is used to being handled. When I pick him up he just sits still. He'll take a bite or two of corn. But I've noticed he is starting to come up and eat off the ground next to me on a regular basis. During the summer the my three Buckeye hens from last year free ranged the farthest from the coop.
All the hens and pullets seem to be compatible. They seem to work out their pecking order without much fuss. I've read the Buckeye are good mousers but I have to say my Australorps win the mousing competitions.