I have both an Indian Ringneck and a Goffin Cockatoo. I would without a doubt recommend a ringneck over a cockatoo.

Ringneacks are smaller size which means a smaller cage. They are generally better talkers. Because they are smaller there is less of an injury if they bite. They are less destructive. Cockatoos are notorious for feather plucking, mine doesn't but I know it is very common. Cockatoos are termites and you can't leave them unattended for even a second (out of their cage), because they are so very destructive. Cockatoos are more expensive than ringnecks, both initially and in the long run. Cockatoos toys need to be bigger than a ringnecks, therefore more expensive, and they destroy their toys much faster. My cockatoo can go through a toy in a day or two, but my ringnecks will last weeks or longer. Cockatoos are also louder. Generally they have a scream off twice a day, first thing in the morning and late at night. My cockatoos screaming usually last about 10-15 minutes, but there have been times she will go on for hours.

I love both my birds and wouldn't want to be without ether of them, but if I were getting one or the other I would get a ringneck.

My ringneck as never bitten anyone, I've even taken him into my sister-in-laws k-3 classroom. My cockatoo doesn't bite too often but has bitten before. I too would suggest getting a baby that has been hand raised, they are less likely to bite. Get to know the bird a little before you buy it, if he is bitty then don't buy him, move on to another bird or another breeder.