I am going to say it is going to be between the RIR and PBR. I have a friend of mine that was selling birds for quite some time and never got a breeding pair of RIR's and had a horrible time trying to get any chicks sold. Being that they are dual purpose makes them an attractive buy.
As much as I love the breeds that are beautiful I think the up and coming breeds will be Red Stars and Black Stars. Good personalities with great laying production.
Im not sure if its one of the most common breeds, but I think silkies are the most beautiful breeds. And I know a lot of people who have them so they must be pretty common.
People who know chickens prefer brown eggs. The Road Island Reds are a really nice breed. I have about 6 to 8 of these guys and I think they are sweet little hens. I had to get rid of the roo though, they are just nasty things.
Leghorns are another nice breed. I have about the same number of these guys. I love my roo, we call him Foghorn Leghorn.
Another nice breed is the Cochin. The hens are sweet and the roo is Gorgous.
I only have ONE barred rock, she is getting really big these days.
The orps are another breed that is fairly nice, but i do not like thier personalities all that much.
I have about 14 "Cinnamon Queens". These are crosses between the RIR and the Leghorns. They are GREAT layers, brown eggs, and they are a sweet hen. i have never seen a roo though.
The plymouth rocks are sweet and nice layers. The roos get enormous and they are gorgous as well.
As far as yard ornaments. I love my polish hens and the roos are simply Remarkable.
The wife loves the silkies and they are a nice, innocent and fun bird to have.
I love Bantams, but the roos i have are not real good for them. I do have a pair of black tails and they stick with themselves.