I think that people are looking for the “right” answer here and there isn’t one. I spent most of my career writing thousands of pages of technical documents in InDesign (started with FrameMaker before that). I hated WORD and really enjoyed those other apps. I developed extremely complicated documents in InDesign with great ease compared what I currently deal with in WORD (which I currently have to use). I also have a strong interest in typography and document design which was supported by InDesign (and not Word).
That being said, I am currently doing more and more in plain text and markdown. I have been persuaded that the process of writing and the process of document design are really two separate things — where, honestly, the former is more important for my job. Further, I am more and more of the belief that doing them at the same time siphons energy from the actual writing (also because the writing is “work” and the document design is “fun” and human nature is what it is). So, once I have the text, THEN, I put it into some word/document processor and make it look nice.
With respect to the longevity issue. I am somewhat torn. I did a lot of slide presentations in PPT in the late 80s early 90s, and a few years ago I wanted to look at them. No way. I could not find a version of PPT anywhere that would open them. I sent them to friends with older versions on PCs and they couldn’t open them. I search around the web. I tried document converter sites like Zamzar, etc. No luck. Eventually I just opened them with BBEdit and extract what text I could and moved on. With the more modern formats using XML this would be unlikely to happen again. But now also have a large library of text and md file that I work on in BBEDIT and feel pretty safe.
I’m bothered by the way they add titles and dates to everything I exported, along with links to the “original document”. Yes, it’s Markdown, but I felt like I didn’t have total control over my own content in those moments. (Not a big deal or a deal breaker; this isn’t the reason I don’t use Craft. It was just something that annoyed me in a small way.)