I agree with other posters that a lot depends on the individual, but I will add the caveat that you can at least increase your odds of getting a certain type of personality by purchasing breeds known to have that type of personality. Not all individuals will necessarily be as the breed is reputed to be, of course, but many will. Their breed has that reputation for a reason.
To add to that, I don't think people who only ever own one or two birds of a specific breed and have bad experiences with them should write that breed off entirely, either, especially if that experience is far removed from the breed's reputation. Sometimes you just get oddballs. An example is that I love my Dorkings,
adore them even, for their docility and sweet personalities, but my girl Kita is a weird one in that she's very high-strung and not much of a people chicken. Had someone only ever gotten one Dorking and it happened to be one like Kita, I could see getting the wrong impression of the breed. Sometimes certain lines are just weird, and trying the same breed from another source, or even a different variety of the same breed, can lead to a totally different experience.
This is one reason why I don't write off Orpingtons as well. I've only had a few, but only one was the sweet and cuddly individual that they're supposed to be. They were one of my favorite breeds because of her, but I've had a few more since and haven't had great experiences with those individuals, so it has kind of lowered my opinion of the breed. I guess that goes along with the theme of the thread. But that doesn't mean I won't try Orpingtons again at some point.
And more to the topic at hand, I was surprised that I didn't end up adoring my Silkies. People talk them up all the time, but I didn't find them to be that great, not even as far as broodies go, and I learned that I just really don't like larger crests so the Silkies really don't do anything for me. That said, they did spark a life-long love of silkied feathering that I thankfully can appease by keeping other silkie-feathered breeds.
Another one that stands out is my Fayoumi. I got a few different white egg laying breeds years and years ago to see if any of them stood out for their personalities, and one of them was an Egyptian Fayoumi. She was a bit of a wild child, all her life really, but once she was an adult she also became quite cuddly, something I hadn't really heard of before in Fayoumis. She's long since passed on and I haven't had another one since, but I was really surprised at how much I ended up liking her while I had her.