Someone told me that she read somewhere Enfamil is the hardest formula to digest but who knows if that is actually true. Seems like every kid (and tummy) is different. We tried a few (Enfamil, Kirkland/Costco brand, Target brand, Nestle,) and then finally went back to and settled on Similac Isomil Soy and seemed to have much less spit-up and gas with that one. However, at about the same time we switched bottles and I really think the Dr. Brown's bottles made a big difference. They have a tube in them that helps the air go to the bottom of the bottle and not to the baby. Maybe give them a try and see if that helps. We have loved them and just bought the Dr. Brown's training/sippy cup to move on to. Hope you find what works for your little one!