I think climate plays into the decision a bit.
I wanted outdoor chickens who would also supply eggs (and I live in Ohio), so Silkies weren't the best way to go. I also didn't want to deal with the extra susceptibility to problems like "seahorse syndrome" and scaly leg mite.
Since I was looking for friendly, docile, quiet birds I settled on Buff Orpingtons as my fantasy birds.
But in the end I purchased hybrid Golden Buffs because I could purchase them vaccinated and "Started"-- it seemed like an easier way to get started with chickens. It's just too expensive to buy the vaccines in 1000 bird vials, and I wanted my pets to live long healthy lives.
It turns out the Golden Buffs are a very quiet, sweet, friendly, and docile option. I love mine (you can see them on the web page listed below). They were great starter birds, and they each now lay an egg every single day (even in freezing cold weather)! Because they are small (about 4 pounds), they can fit in smaller housing. My next three birds (maybe in a year or so) will be a Buff Orpington, a Silver Laced Wyandotte, and a Speckled Sussex, all friendly and docile birds. But I'm glad I started with my super-sweet Golden Buffs.
Pet owners can't go wrong with Meyer Hatchery, which has a small order program (minimum three chicks) and sells three kinds of started birds. They have a nice catalog and a super helpful staff.