I was so exhausted by the trial and error process that I had to undergo with my second baby when he would not take milk from any bottles because he would either get colicky or he disliked the teat. I never had that much of a problem with my first child with whom I used Avant milk bottles. But then again he didn't take to breastfeeding that well and preferred the bottle from the start. Whereas, with my second one I had breastfeed him up until 7 months and then needed to wean him off as I was returning back to work.
It was only with Dr Brown bottles and teats that he would take his formula milk and not have any problems with being too gassy, windy or colicky. I think the Dr Brown teats are softer and bottle mechanism mimics breastfeeding experience the closest.
However, the only gripes that I have with this brand are: there are a lot of bits and pieces to wash before sterilising, more expensive and it tends to leak. The latter I don't have much of an issue with now as I use the feeder stopper when preparing the milk so it hardly ever leaks now.
But these gripes of mine are minor and pale in comparison to the benefits these milk bottles provide for my son. As I have a mantra; 'A happy baby makes a happy mummy, a grumpy, sad baby makes a even grumpier, sadder mummy'.