Personally, I would recommend a baby ball python. Just like any other pet, if you get a bp when its a baby, it will grow acustom easier and (probably) be more docile as it grows because obviously, it will know you. However, I don't think you would have a problem with a older ball python either (unless of course it is wild caught).

I think there is also something to be said about actually watching your ball python grow and mature. I think its an awesome experience which will bring you closer to your pet. Hope this helps.