My experience with hot three females has been excellent. My favorite bird is a hot 3 female. She's got a little bit of attitude, but its not major aggression. Females can vary with some being more aggressive. My Diva is very laid back for an amazon. Her mother who I originally got as a 13 year old adult had a little more attitude. Ellie sometimes bites me if the dog sticks her nose too close, or if she is standing on me and doesn't like the way another bird is looking at her. The classic female amazon bite situation isn't really directed at the owner. Its directed at someone else, but the owner is closest, so they will use our flesh as a demonstration to another person or animal. Females can be nasty and down right dangerous toward other birds.
My male napes have been a little less aggressive toward other birds, but more territorial and more prone periods of general outrageous aggression at maturity. So far I have not had a female experience major aggression at maturity. Just as with any bird, the girls will grow up and get more opinionated. But I haven't seen anything that I would call strictly hormonal aggression.
I can't speak to birds switching favorites. I think any bird can do that, but I'm single, so mine don't have a choice. Regarding shipping vs. visiting, I think the connection experienced when the bird first picks you tends to be more on the human end than the bird's end. I've had outstanding relationships with birds that I've had shipped and that I've had to work for. Sometimes when you ship a bird, they are disoriented, a little defensive and you don't know what your getting, so your less confident. Then if the bird doesn't step out of the carrier and act sweet as pie, doubt tends to creep into the new owners brain and fester. If your willing to work with the bird and build the relationship, long term I don't see a difference in visiting first or shipping. Short term, if you visit first, your likely to be a little more confident in your handling abilities, and you'll know what kind of handling works with that bird. Its still might be defensive or scared when you take it to a new home, but the owner tends to be a little more confident and likely to stick with it. Especially if they believe the bird picked them.
Thats just my experience. I've shipped a few babies and all but one really liked the bird. Although a couple said they had to go slow. One person felt the bird didn't like them and rehomed it. Honestly, I think she could have worked with it, but she was unwilling.
Melissa