L.-
My pediatrician told me when I had my first son that I could buy any formula, whatever was on sale, as long as it had iron in it. I did that, and never had a problem with any store brand or name brand. (I used lots of those enfamil and similac checks that you can sign up for). When he was about 10 months, Sam's Club came out with their store brand and I LOVED it. It was the cheapest and mixed up fine. My younger son had reflux, so we had to use soy and I started with Sam's Club right away. Unfortunately, Sam's stopped carrying the soy, so I went back to buying whatever was on sale. The store brands from Meijer, Target, and Wal-Mart are all the same price, so I just buy wherever I am at. My son has accepted all of them just fine (and he has a more irritable stomach than my first) but I noticed that the Target brand doesn't mix up as easily... I always seem to have clumps in the bottle. All of the formulas are FDA approved and if you compare label to label, some have more vitamins or minerals than others and vice versa, but they are all comparable.
-A.