Did you know there is a lot of technology that goes into a baby's feeding bottle? I was totally ignorant. To me, a bottle is just a bottle, no big deal. So we bought whatever bottles we came across, looking at just the nice little designs as a criteria of purchase.
Then we learned that the teats play an important role in helping to reduce colic in a baby. A lot of premium brands offer teats with special air system that releases the air so that baby doesn't suck it back in.

We started buying these special teats from NUK. The shape is made to be as close to a mother's nipple as possible, and it supposedly has some benefits in shaping the gums for future tooth growth too.

I also bought some Avent bottles to replace our Pureen ones. These bottles came with Avent's teats which also come with some air system technology. However, baby was already accustomed to NUK's teats and didn't like the slower milk flow of the Avent teats. So I had to purchase more NUK teats in replacement of the Avent ones.
I'm now feeding with more confidence knowing that baby's getting what's best for him.