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well I have a green cheek conure( which is similar to a sun conure) and I have cockatiels i think that Sun conures you be more intelegent(smarter) then cockatiels. The cockatiels I have they are like semi tame a little, they are smart but you know they are a little lost and a little dumb at times but my green cheek conure (tamed) is very smart. im not sure if its because he tamed and the cockatiels arnt but thats my personal experience. But for noise I have heard they are extremely loud as i have also made this decision on what bird to get but are playful,cute. As for cockatiels they are not really so called "loud" because they whistling is actually nice to hear. I remember hearing that A male cockatiel is a better whistler or talker (even though there bad talkers and hardly ever talk) then a female but a female is more cuddlier and that means it'll probaly make it a better companion and more attached to you but the truth is every bird has its own individual personality just like humans do. if you want my decision i think if your actually going to dedicate time and if its going to be tame and like your best freind then i would probaly get a sun conure but if not and you want to get a bird for just showing off like what some people do so it can talk and stuff because it is cool then dont get one because you know they have feelings and a soul but by the way it looks like i think you want one as a companion (freind) and you will look after it and at the end of the day its your decision.

I remember when I was deciding to get a bird it was between a Galah Cockatoo and A green cheek conure, I kept changing my mind but then at the end I got a Pineapple green cheek conure but guess what about a few months later I found a Tamed Galah who was attacked by something and was horrified, i thought it was going to die, well it survived and now I got a green cheek conure and a Galah cockatoo (thanks god).

Good luck deciding.