When my son was first born I didn't have a clue what formula to start him out on. When I mentioned to the hospital that I was on WIC, they started him out on Enfamil Lipil with Iron. That didn't go well for the little guy. He got horribly constipated to the point that he strained and cried. It was horrible.
Then WIC switched him to Enfamil Lipil Gentlease for babies with fussiness and gas and he has thrived ever since. He hasn't been constipated since we switched to the Gentlease and he's grown to be a healthy, plump, 9-month-old. Gentlease was my savior and he's been so much happier ever since.
We tried to switch him to the Parents choice Gentle because it was cheaper but that didn't go well and caused him to spit up more often. I continue to be very happy with Gentlease with the only downside being the price. My advise to parents is, once you find a formula that works for your baby, stick with it. The reward of having a good formula is priceless.