We adopted an adult cat (she was 2). Cats Protection wanted us to have an adult because ds was then five, and they don't like to place kittens with young children if they can avoid.
I was very pleased to have a cat who was already litter trained and had gone through the 'mad charging about in the middle of the night' phase (she still does that, but like a teenager has her own key to the door and so lets herself in when she's ready for a kip!).
I think Cats Protection find it harder to re-home cats (and ours is a black cat too, so very hard for them to place). She is not hugely affectionate, won't sit on a lap or anything, but she has been a blessing to us.
Con - well, you miss the super-cute kitten phase, and of course as an adult rescue she is the one who went through something bad which led to her leaving her first home and living rough with her litter. She gets away with murder though as DH is convinced she has PTSD or something! (She doesn't at all).