I don't know much about the white cockatoos(about as much as the average parrot obsessed person). But I do know a whole bunch about galahs.
Galahs are amazing, intelligent, social, and are my favorite of the cockatoos. Tend to be a little more mentally stable, and more independent than the white cockatoos. But that doesn't mean they are totally easy, they tend to be sensitive and have can have their feelings hurt. If not socialized well they can develop phobias, neurotic behavior, and self mutilation/plucking(not as commonly as the white 'toos) It seems to me like phobias in well adjusted birds often starts around puberty for some reason, maybe because parronts start slacking off with socialization after a couple years thinking their birds are good to go for the rest of their lives. Socializing something that needs to be done often, all the way through puberty. Once they are fully mature you can slow down a little, but never completely stopped.
Galahs love to learn tricks, and are generally very eager to trick train. Mental stimulation is something all parrots should have, and trick training is a amazing way to achieve this.
Galahs are highly prone to fatty liver disease, fatty tumors, obesity, and heart disease. They are designed to live in a harsh enviroment, are AMAZING fliers, and are designed to use a lot of energy daily while living in a enviroment that may not always have a good source of food. Galahs live in all but the very driest and wettest areas of Australia. One of the few parrot species that lives in the desert.
If you want a galah you should take a commitment to keep it fully flighted, and also
motivated to fly. Without flight many galahs die of fatty liver disease, or other fat related illnesses between 30-40 years of age. Some galahs start developing fatty liver five years of age or younger. This is a bird that can live 65+ years!!!
Don't feel restricted because of a bird being able to fly, harness train them and you can take them out. Here's my galah flying in her harness :heart:
There's my little rant about galahs needing to be kept flighted haha