UL I have no interest in shooting any one down. Just trying to help. If you want to shoot BIF then you need a lens with a blistering fast AF like the cannon 400L 5.6. I think you just picked the wrong photos to make your point. Tokina, Tamron and Sigma all make nice glass. In the Focal range/price point the OP is asking about though I think he's better off with Canon.
You might want to clean your sensor if you haven't since you took theese images. There are a lot of dust spots. Especially #2 and 3.
