Orpingtons, Brahmas, Cochins are heavy feathered breeds. Breeds that do well in cool weather are the Plymouth Rocks, Rhode Island Reds and Wyandottes. The Leghorn, Minorca, Andalusian, Hamburgs and other Mediterranean Breeds will do better in warmer weather. The crested varieties may have problems with freezing head feathers. Rose combed birds are also a better choice for colder weather as the Single Comb is vulnerable to freezing.
Bantams are miniature chickens.
Your reasons for selecting one breed of bantam would be similar to how you select your breed of chickens. However, you are more likely to be choosing bantams for other reasons than for food or egg production. Bantams are often selected for ornamental reasons or the fact that a person can raise more birds in a smaller space than would be possible if you were to have a large fowl of the same breed. Bantams still lay eggs - the eggs are just smaller. Turkeys are raised for the table.