The thing is that these operating systems have frequent major updates, so whatever article I do, it will be obsolete soon.
They're not updated that often, there's roughly a major release every 12-18 months.
All the minor updates in-between are rarely all that interesting.
I think just a feature comparison could be interesting, doesn't have to go too deep into everything.
Maybe do an overview at the different software available as well, since this is what I presume you mean that it's can't compete, since QNAP and Synology have been around so much longer that they've built up a more solid first and third party add-on catalogue?
That's also where most open source options can't compete, even though you could most likely make a lot of things work, it would be up to you to make it work.
Then again, Docker solves this problem to a degree.