Hi,
I got the Dr. Brown bottles because my kids both were very "gassy." I don't know if they worked really because I didn't use a whole lot of other bottles to compare them. The reason why I am writing is to suggest that you register for both (a few Dr. Browns, say 3 0-3 month, and some Avent). That way you can compare.
The avent are nice since they can convert to sippy cups later and their hand held breastpump works really well as long as you boil all of the pump parts before using it.
Two more things about Dr. Browns: they have more parts and take longer to clean and and I found that they leaked. I put up with all of that because I hoped I was helping my kids gas pain, but I really don't know.
I have heard good things about the soothie bottles, like the pacifiers that hospitals give out. I didn't get to use them since my kids were done with bottles when these came out, but you may want to register for a few of these bottles, too.
Holly M.