I have also seen this Reddit and mostly what I see out there are students who are trying to just enough to pass an exam. This question is one that has been asked and promulgated by course writers and developers since long before any of this has been a thing.
I've commented on this before - are we trying to "pass a test" or are we trying to acquire the skills and knowledge to do a job. This is the first question. I don't need to go into a diatribe about motivations, but suffices to say, those on the CompTIA reddit usually are trying to pass a test so they can score a job of some kind, not trying to build up a career.
So now, the question is - what is certification about, to pass a test or validate knowledge?
Now, if we believe in the spirit of what certification is about, then restricting one's learning to one book, no matter how good it is, is not wise. A prudent learner is going to investigate different approaches, writing and learning styles, and adapt those to how they learn. They won't ask the question about which book is better at preparing for an exam - they'll ask for more books, more materials, more perspectives.
But the OP's question is, "because of time/money, we have to choose one book, teach it once, and get the candidate to certification ready status". Maybe I'm misrepresenting, but that seems to jive with the posts on the Reddit sub, as well as my experiences with folks who just want the cert, not the knowledge. I personally have found this to be a bridge too far.
It takes time and multiple resources to get to certification status. But I believe as long as we promote these "get certified fast" initiatives, we do a disservice to what the certification represents.
Just my 2¢...
/r