Good question! I recommend simplified first to the average reader because most people who start learning Chinese will never learn both simplified and traditional (which is the natural destination, in my opinion). Given that they only have so much time to spend on reading and writing, and that most will quit well before they become literate, I think there’s a compelling case to focus on the most useful set first, and that is simplified, mostly because the number of users is an order of magnitude larger. That’s not true if you know you’ll go to Taiwan, for example, which is why I mentioned that in the article.

The conclusion might be different if your goal is to study the writing system itself or if I knew in advance you’d go all the way and learn both traditional and simplified. Then I would recommend learning traditional first, mostly because traditional characters just generally make more sense and there isn’t an extra layer of obfuscation covering some characters (I’m thinking of things like simplifying tons of completely unrelated components to 又, for example). I don’t know your background and how much of this you know already, but if you’re curious, check out this article by Ash Henson from Outlier Linguistics: Are simplified characters really simpler to learn?

Finally, let’s consider learning both at once. Chinese language education in general already has a strong bias towards the written language and it’s not uncommon for students (especially at university) to spend a disproportionate amount of time with characters. While it would be interesting and helpful for acquiring characters if they learnt both sets at once, this would increase the overall time spent with characters, which I think is unacceptable if the goal is communicative ability across the board, not just reading and writing.