I have read that Enfamil Lipil is supposed to be the most like breast milk. However, you may find that if you do have to supplement/feed formula, that your baby is better on one brand rather then the other. A good example, I had to Formula Feed, and when I did I started on Enfamil Infant Premium, my LO didn't tolerate it well, and I switched to Simply Right (Sam's club's brand) Gentle. She loves this. However we were in the hospital over the weekend, and all they had was Enfamil Gentlease, and she didn't like it AT ALL, and gave her horrible stomach issues.
My SIL's little one hates Similac, and will only eat Gerber.
So really, there isn't a ton to research, you can start with one type, I really do recommend a store brand, they are soooo much cheaper and the same thing, and if that doesn't work, keep trying until you find one that does.