These two strategies are often used together but are not the same thing.
You can send advertising content or appeals to your opt-in email lists. That’s permission-based marketing, but not necessarily content they find especially relevant and meaningful themselves. Sending it is more in your self-interest, even though you have permission to do so.
You can also use content marketing without an opt-in mailing list. For example, when you add great content your website, people can find it and read it without being opted-in to any mailing list.
The sweet spot is when these two strategies work together. You send great content that keeps people on your lists, which allows you to also send them advertising or appeals.