Unless you plan to breed or show your birds, you'll probably be happier with a flock of mixed breeds. If you choose breeds carefully, It will be easier to tell the chickens apart as individuals, tell who's laying well, who's laying poorly, and who's laying abnormal eggs. You can also plan for steadier year round egg production, and for one or two broody prone hens to hatch eggs and raise chicks, while the rest of the flock lays well.
It's getting chilly outside. But that doesn't have to mean frozen combs and wattles, painful toes, and unhappy hens. Keeping chickens happy through the winter just takes a little bit of extra attention.