Number 1: Personality.
I like my chickens to be a very outgoing breed. Loving being around people, and other animals like our family dog. Now many chickens can be trained/adapt to being more friendly, however some chickens are naturally timid, so I do my best to avoid those chickens. Most times, it has to deal with the individual chicken itself, so don't rule out a breed because when you google it it says, timid, not used to people, etc.
Number 2: Egg Laying Efficiency
I could never bring myself to butcher one of our chickens because to me they are family. So I find it important that they at least provide us with eggs. Now, even when my girls reach the point where they stop laying, they will stay in the family until they are taken by natural causes. But from what I've read/heard, they can lay for a very long time
Number 3: Color/Style
I would love to have myself a big puffy silkie someday but for the time being I pick my chickens based on their color. For some reason the Rhode Island Red hen intrigues me and I love the deep red/brown color. Not only do I love the color but also the consistency of laying and their winter toughness,
Now, I'm not saying that you should come read through my Ramble before going for a new chicken, but these are three factors that are important to me personally, and also to someone who maybe treats their chickens more as pets than just free eggs for a while followed by a chicken dinner. I am at the moment in the hunt for new chickens because we recently lost two and are down to one. These are just a few factors of the many I've considered and I'm not a chicken "veteran" as I like to call it. I'm fairly new to having birds but am loving every minute of it.
Anyways, thanks for reading!