Comment by ghaff
The advantage of a publisher like Apress or O'Reilly is a lot of people still attach probably excessive value to the publisher pedigree.
The downside, as you say, is that they control length, format, pricing, deadlines, etc.
I went through the publisher route once through two editions and, on net, I'm glad I did but I've also self-published in no small part because I'd rather write some more bite-size books on narrow topics and I want to be able to do whatever I want with the material on the schedule I choose.
I agree. Being published by a big name gives you some credibility right away. The issue I personally had with the publisher I signed with (one that you mentioned) is the quality of their products. And I don't mean this specific publisher: it's the whole industry that is mostly broken. I'm not even talking about the content here, only the presentation.
Most publishers can't provide good syntax highlighting for their programming books: mine didn't provide any (we're in 2024 and it's supposedly their domain of expertise so I'm baffled), and their ePub books are generally almost unreadable. I didn't want to make my readers pay $35 or $40 for a book that doesn't provide the basics of what you could expect from a programming book. In my case, the challenge was even bigger cause my book is about two programming languages and I needed syntax highlighting for both and a different theme for each. I don't think I've seen this anywhere yet in the "professional" programming book industry.