I found that I had to supplement with formula because I couldn't pump enough to keep up with T while I was at work. T had a dairy sensitivity when he was a baby (which meant I couldn't eat dairy either, since I was breastfeeding him - fun times!) so we used a soy based formula. We used Similac Soy. It never seemed to hurt his tummy, and that combined with some breastmilk every day served to make him into a big honking 95th percentile boy by the time he was 6 mos old.
I don't know that one is better than others. I would think they would all have to meet certain requirements. I've seen some a little cheaper than others but thats about it. We used Similac with Tony. The hospital gave us Enfamil and he wanted nothing to do with it. So when we got him home we switched and he was fine with the regular Similac formula. So I think thats what we will go with to start and see how things go.
I think it just depends on what works best for your baby. I used Good Start with my first because that's what they gave him in the hospital and then I just kept with it. They say not to change formulas unless your baby isn't tolerating one (doesn't like it, spits up a LOT, milk intolerance, etc.).
I think Enfamil is one of the cheaper ones, and there are Walmart brand ones that are similar to Enfamil so they're even cheaper.
I think it somewhat depends on the baby-some babies are intolerant of some types of formula but I dont think it is so much the brand as the type (soy vs. regular for example). We didn't use formula until DD was close to a year old when my supply started to dry up. We used whatever the samples were that we got from the hospital (don't remember if it was Similac or Enfamil) then I used Meijer brand since it was a little cheaper.
We used Similac Organic liquid to supplement until DS was 9 months old, then switched to the Costco powdered store brand til he was a year old.
I started with similar from hospital and she ended up super gassy. I switched to good start and loved it and will start there this time. I would be careful starting with soy because it lacks proteins that are needed and is only usually suggested when there is an intolerance
They all have to meet standards and are all pretty close to the same. I think you feel like you need one of the big name brands at first, then get over that, lol. Like some ladies said, some babies do tolerate some better than others. DS had a really sensitive stomach and most formula made him really gassy. This time around, if we need to supplement, I think I'm going to go with one of the formulas with probiotics in it. We've had success using probiotics on DS's tummy issues later in life, so we're hoping a probiotic formula might do the trick this time ... assuming we need formula and assuming she has the same tummy issues as DS. If she doesn't, we'll probably just use whatever samples we have.