Essentially all peanut butter is comprised of just peanuts and oil. Then many brands will add in sugars, salt, or extra oils to keep their signature blend smooth and perfectly emulsified and flavorful. The main thing you need to consider is simply the "regular" or "natural" designation. For everything other than baking, I use natural peanut butter purchased in bulk. It tends to be thinner than "regular" peanut butter at room temperature, and can separate more easily into the oil and peanut components. I love that it doesn't have any added fillers or sweeteners and just deal with the fact that it needs an extra stir every now and again.
However for baking, I must admit that I use "regular" brands like Skippy or Jiff. I look for a variety without added sugar or salt, so it's as close to the natural state as possible. Why do I go this route if for everything else I choose natural? The oils that separate out in the natural brands usually cause my cookies and bars to spread or just not bake up perfectly. I wish this weren't the case but it is. If you're set on using natural butters anyway, you should plan to increase your baking time just a touch to account for the additional liquid in your peanut butter.
What's your favorite peanut butter to bake with?
(Image: Megan Gordon)