The question is, which of these things do you need more?
Alternate day fasting: a focus on building a habit! Often people find that just doing a one off fast doesn’t help them as much with their long term weight loss because their not developing long term disciplined habits.
96 hour fast: a focus on results! You may find inspiration with how fast you start seeing the difference. THIS is what I love. This is what starts giving you the more major atophagy benefits.
My recommendation: go with the ADF. As much as I love the thrill of a big fast, there will be plenty of time for that. Showing yourself that you can be consistent and become used to the habit will be incredible for you.