I must admit after having Ari from a baby and seeing the personality change I am more inclined to go with an older bird rather than get a baby. I don't think I could deal with getting another bird and having a dramatic personality shift at puberty. But I also must admit that I would be trepidatious of what sort of neuroses or bad habits would come along with the bird. These are commonly why birds are rehomed.
All birds come with that risk though--- If an adult bird picks a person, it generally sticks to some extent. I would bring everyone along if you are looking and remember, an adult bird (as Ari demonstrated) can show strong preferences toward a specific person, where a baby tends to be cooler with everyone, but rarely does that actually last. I am not saying all adult birds are one-person birds, but some are, and they definitely are programmed to find a mate, so you want to shoot for a bird that seems somewhat sociable if you can and just remember that a sociable baby doesn't necessarily mean a sociable adult. Even if a bird doesn't like everyone in the family, some will learn to accept others with time. That having been said, there is always the risk of jealously etc with any bird post-puberty--the babies get there eventually too.
If you get a baby, it's easy to create your own bad habits..
Birds can develop neuroses even when well cared for well...and lots of birds at rescues are there because their owners died or went to college etc (it's not always behavioral)
I am not saying that hanging out at a rescue gives you a complete picture of a bird (because obviously rescues are high-stimulation environments when compared to a home) and any environmental change will often freak a bird out for a period of time....especially during that "building trust" period...BUT, if you talk to the rescue people and visit often, you can get a semi-decent idea of what many birds will be like (excluding those with super high needs for attention/action etc, because a rescue is way more active than a home..and because certain birds put on a show for attention, even if they don't actually like you that much lol).
The key with an adult is trust and patience-- You probably need to figure out the whole out-of-cage situation if you are getting an adult, because with them, they aren't going to trust as quickly as a baby, and sometimes that can take months....A younger baby is going to let you touch it more easily in many instances, but an adult bird is still going to need to get out and about (even if it won't step up). So if you do get an older baby or an adult, I would make sure you have a plan regarding how to safely let it out (because again, building trust can take longer, but you don't want them getting super neurotic about their cage in the meantime). Even an adult bird that picks you MAY be more hesitant in a new environment, so just keep that in mind.
Also, remember the importance of a 45 day quarantine in a separate space, and the fact that a new bird may upset your other birds etc.
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