What is your favorite bottle? Our baby doesn't really have gas issues, so I'd like a bottle without too many parts. We tried Dr Brown's and Born Free, but baby doesn't really like them, plus they have a lot of parts. I almost tried the Playtex Drop-Ins but read some reviews that it's hard to tell how much baby has eaten which is important to us right now. I've heard Avent tend to leak. I'd like a bottle that comes in a 4oz, 6oz, 8oz sizes if possible.