PreTexts is a nice system and I have a great deal of respect for their developers. Its only issue (my perspective) is that it is a bit complex for the average author. We based our infrastructure around Wikis that are more easily mastered although the same level of complexe content can be made on our system as theirs.
We both use mathjax as our equation renderer.
They have a few more powerful export options than us, but we are growing to make up the difference.
We can harvest from PreTexts books, but there is little benefit from using them vs. our infrastructure unless it "calls" to you. We both have the same goal.
