Pros for major mitchell...
- Beautiful, probably the most attractive cockatoo species
- Bonds very deeply to one person (potentially a great pet for a long term single person who works from home or can take their bird to work)
- Very sweet, makes cute little cooing noises
- Highly intelligent and emotional... large 'too personality in a little package
Cons...
- Can be very loud, very regularly especially when alarmed
- Requires a lot of work to keep them well socialised and well adjusted
- Can become aggressive and most are generally nippy birds (they are nippy with each other in the wild as well, its just their natural state of being another way for them to communicate their feelings and they often like their space)
- Do not like being left alone
- Do not like sharing their person with anyone and can develop issues with biting their owners or others. You must have an understanding partner/family lol
- Need constant stimulation to keep them busy because they are so intelligent
- Can be flighty/phobic
They aren't as cuddley as other cockatoos as well, Im not sure if you would put that in pros or cons... some in fact dont like being touched what so ever. Some also never learn to talk or mimic what so ever and those that do are not as good at talking as a lot of other 'too species (they have a cute little squeeky budgie voice lol) I have included some video of majors so you can get a contrast in temperament. Comparing galahs and majors is like comparing apples and oranges

My galah is like a dog, follows us everywhere and loves being on the ground.
These videos arent fantastic indications of their temperament as a pet, but they arent really the kind of bird that does cute or exciting things to post on youtube. But their interactions with each other will give you an idea of what I mean by nippy... its something you would have to accept about them, they don't give as much body language as other small 'toos... they are like a large 'too in that way, a nip might be the first thing you notice. Basically they arent a bird anyone would recommend for someone looking for a great temperament... but if you can accept you may end up with a noisy, nippy, bossy bird that is beautiful... and are willing to put the work in to keep them entertained and well socialised... then you should be fine.
If you are still wondering at all it means you have your heart set on the major, because anyone who wants a bird based on good temperament would go for the galah no questions asked
So... ask yourself... will you love your bird regardless of biting, screaming and possible jealousy issues? If you are concerned about any of those things, do not even consider a major any longer because the fact is, there is a good chance the bird will have one or all of those issues. You would be lucky to get one without any issues at maturity. Keep in mind, they are sweet as pie as babies, but come breeding age and especially at breeding season you need to accept your bird wont be a sweet innocent little baby anymore.
[ame=http://www.youtube.com/watch?v=3uAaTe_W5to]Major Mitchell Cockatoos - YouTube[/ame]
[ame=http://www.youtube.com/watch?v=0I-4nU_6_l0]Major Mitchell Cockatoos (13) - YouTube[/ame]
[ame=http://www.youtube.com/watch?v=VWPqsFncz4k]Sal the Major Mitchell Cockatoo - YouTube[/ame]
[ame=http://www.youtube.com/watch?v=8Mt6WpS6e0s]ã¾ã£ãŸã‚Šã‚¯ãƒ«ãƒžã‚µã‚« - YouTube[/ame]
[ame=http://www.youtube.com/watch?v=u5XV5CUZJsQ]Major Mitchell parrot cockatoo Kuki - YouTube[/ame]
(some of these poor birds are in such tiny cages D: heart breaking)