First, I want to say that I'm about to express my opinions. I came by them through intense research, study, and observation of my own birds, but there are many people out there who disagree with me and whom I still deeply respect. This is one of those topics that can get ugly because we all want what's best for our birds, but let's all be sure to play nice
There is a lot more to the clipping/not clipping debate than most people realize, and one of those key factors is AGE. A bird who is properly fledged and given lots of time to become an expert flier when his feathers first grow in is leaps and bounds ahead of his counterparts. This is something that makes many people defensive, but that is not what I want. I wish everyone could see the difference in two sibling birds of any species, raised exactly the same way, except that one was allowed to fly for at least eight weeks (more if they are larger) before being clipped. The difference in intellect, temperament, and confidence is stunning. It's a developmental thing. Learning to fly is hard and complicated, and mastering it builds some incredible thought pathways in the brain of a bird. Also, clipping a young bird before full fledging usually leads to that bird being a terrible flier for the rest of his life, thus increasing the risk of injury later on if you or another owner decides to let him fly.
Clipping also removes the "flight" option from the famous "fight or flight" question, or as I like to call it in birds "flight or bite" leaving well, only "bite" as an option when they are frightened. When a bird is too young when given his first clip, this can actually stunt his development so that "bite" is the only option he knows, and he will bite whenever he feels threatened.
I also feel that in many cases having a bird that can fly is safer, as they can get themselves out of harms way faster BUT THAT REALLY DEPENDS ON THE HOME! Some homes have kids who leave doors open, parents who leave ceiling fans on, etc. other homes have predators and flight is safer. What I'm saying is, one all inclusive "clipping is safest" or "flighted is safest" is naive. Each family needs to evaluate their own risks, but PLEASE don't clip babies.
Do I clip?
Yes, but I prefer flight.
-Mel is 100% flightless, I don't think she has ever been clipped. When something startles her she flies to me.
-Battle is also an expert flier and uses that skill to fly to the nearest man for scritches; the little hussy!
-All of my cockatiels and budgies are flighted, though not all are tame. I had the tiels in a big flight cage to exercise until a low down rotten thief came and stole a bunch of birds.
-Cache was clipped very short for her first year of life. She is incredibly phobic because of it and will not allow flight feathers to grow in.
-Flick is a sweetheart when clipped and a beast when flighted. We clip her.
-Tex has never flown as far as I know, and he is also phobic. I can't wait for him to molt.
-Sam and Lady both have all their feathers but both were clipped as babies I think, both fly only when startled, and hey fly BADLY and crash.
Basically what I'm saying is not only is it a personal choice for safety, it is also bird by bird, situation by situation. I wish every bird I own could have full flight because I see how they love to fly, but some cannot.