I remember when I was debating the two also because most people that I knew who took seismic swore by Hiner.
After reading several reviews and also talking to a few friends who took AEI, I went with AEI's course. One reason being that I liked that AEI videos were unlimited (meaning you could rewatch them as needed), whereas Hiner's was limited on something like 40 hours.
My experience with AEI was great, considering I was able to pass the exam on my first attempt and I have no structural/seismic background. Everyone's experience is different since I do know people who weren't able to pass with AEI or Hiner.
I really liked AEI but I put in the work, so be prepared to put in the hours to watch all the lectures, do all the workshop problems/quizzes, and you will be set up for success. I felt like the AEI workbook truly had everything you needed to bring into the exam, minus a couple PDFs that they provide you that you should print out and put in a separate thin binder with your cheat sheets.
The instructor is also very thorough with his videos and is easy to reach out to if you have any questions.
I also had Hiner's workbook but only looked through the practice problems/exam in the back. If you compare the two workbooks, you will find differences in some of the formulas because of the different approaches, so I wouldn't recommend trying to learn both because you'll confuse yourself. It also seems like with Hiner you will need to supplement with other materials.