It depends to a degree on what kind of birth you want. I'm really glad we're taking a class, but I'm planning on a natural birth, and the class gives a lot of practical natural birth advice - we practice positions with an instructor there to help make sure we're doing it right, we had a doula in to teach DH counterpressure techniques, and so on. You never know what will happen, but if you plan to go to the hospital and get an immediate epidural, that kind of thing may not be as important to you. There's nothing in the class so far that I think we wouldn't be able to find on Youtube, I just strongly prefer the hands-on approach and correction. The non-hands on stuff, like learning about stages of labor and induction methods, could easily be read on the internet or in a book. We're only halfway through, so we haven't yet covered medical pain relief and baby care, so I don't know how useful those classes will be.
In the end, it comes down to learning style and personality, as well as your birth goals. If you decide to DIY it, make sure your birth partner is right there next to you watching videos! My DH is learning more than I am in class.
