A benefit to the discbound journals is the ability to add in any pages you want. You could buy a fancy punch to do this. (We use these ones.) Or you can follow these steps for a more affordable option.
There are plenty of different types of notebooks out there. As the office supply nerd that I am, I've tried a lot of them. But in the end I've found that discbound journals are the best for managing all of my D&D campaigns. In fact, the benefits of my discbound campaign journal are numerous. Let's take a look at why.