In the UK, they are pretty much all the same, though your baby may prefer one over the other. When we moved on from breastfeeding, we started with Cow and Gate, which worked fine, but I wanted to use Hipp Organic instead. We switched to Hipp and it caused my daughter to have horrible reflux and projectile vomiting after every feed for a week (until it occurred to me that it was probably the new formula that had caused it). We switched back to Cow and Gate and that worked great until we were ready to move on to cow's milk.
My daughter accepted it with no problems, though she did always prefer the ready-to-feed cartons rather than the powder. It does taste a lot better (tastes like soya milk to me whereas the powdered version tastes like rotting cabbage!). If you have trouble getting your LO to accept a bottle, you might try the RTF version in case he/she takes to it better. The powder cartons also have a shelf life of a few weeks once opened (I went through one a week once FF full-time), so if it's only going to be for an occasional bottle, you might find the cartons cause less waste if you aren't going to make it through a whole one before it expires.