Unless you have specific medical needs, like a hypoallergenic one or something to deal with reflux, they really are all the same, despite their marketing attempts to convince you otherwise. Some will suit one baby better than others, but there is no way to know for sure what that will be until you try. I would pick one that you can afford (there is slight variation in price between brands) and that you can easily buy where you normally do your weekly shop and just see how it goes.
We used Cow & Gate. It's exactly the same as Aptamil (same ingredients and same manufacturer), but it's cheaper as it's branded slightly differently. We tried SMA when my daughter was in hospital under a great deal of duress as I was breastfeeding and really wanted BF support, but the midwives were really negative and just wanted us to FF. So that's what we started on and it was just such an awful experience (I mean dealing with the stress of the midwives trying to push us not to BF) that I just couldn't actually use SMA. It's perfectly fine, though can be more constipating than other brands, but I just hated it because I had such a negative experience with it. We also tried Hipp Organic, which is considerably more expensive than the others, because it's supposed to be more 'gentle' but it gave my daughter horrible reflux, projectile vomiting after every feed and screaming in pain. So we tried Cow & Gate and that was great, no more reflux, and no other issues, so that's what we used. Really just pick something and try it. You'll know soon enough if it works for you.
