We've tried a couple different ones so far because at first it's wise to experiment and see before going crazy with the most expensive soy-based specialty formula, ya know? (We had friends whose pediatrician told them what to use and they are paying through the nose for this stuff.) Believe me, before Ian was born I read labels and compared notes so I know it's the same damn ingredients...possibly with the exception of a few proprietary combinations. But still, the nutrients are the same. Period. It IS all a matter of what works with the child's tummy.
We started with Enfamil Lipil because I had a sample and we hadn't gotten the other kind yet. Parent's choice and their Sam's club equivalent both have comparable options:
Parent's Choice milk-based regular and organic and Member's Mark infant formula have DHA & ARA plus Iron. I've noticed the Organic version of Paren'ts Choice mixes a little foamier, which was a bit disconcerting to me. But I suspect that is where the bottles come in (in terms of keeping the gas down). I didn't notice a difference and my little guy didn't have issues with any of them. Sam's club also has a "Gentle" infant formula with partially broken down whey protein for fussy/gassy infants. So there are options. It also depends on if you have Sam's club and a membership. The great thing about Parent's Choice, though, is that Walmart is everywhere. And even though I don't like it on principle, heh, I can't argue with the fact that the price is SO much better.
Note: For all the types I've mentioned, we put warm filtered tap water in a bottle (Avent bottles, which I love- I purchased the microwave sterilizer, which has become my insurance policy for cleanliness - it was worth every penny) and put the dry formula in and then shake 'em up. I do 6 bottles at a time (which is what the sterilizer holds) and put them in the fridge. I've also discovered our good eater takes them cold without issue, so warming them isn't necessary. I will often take the bottle out of the fridge about a 1/2 hour prior to feeding and if we have the time (and he isn't starving) I will use the warmer or just do a homemade "warmer" by putting water in a big mug up to the formula level line (when the bottle is submerged). Take the bottle out, microwave the water for a couple minutes until really hot. Set the bottle in and let the water distribute the heat evenly. (It's never recommended to microwave the actual bottle of formula, though I know some do it.)
As you can see, I've gotten this whole formula thing down to a science.
Ask me about how we created a cooler from our insulated free Similac diaper bag by using ice packs so we can keep a set of bottles upstairs for nighttime feedings.