Science is built like a wall and each contribution (book, chapter, paper, data, model, idea, thesis, anti-thesis, paradox, and even, inconsistency and imposture...) represents in science "Another Brick In The Wall", Dixit Pink Floyd. And as such, this brick only makes sense if other bricks can lean against it. The same applies to academic research, which, as "a brick in the wall", should support new research works. Thus, IMHO, academic citations could represent a fair measure of the value of whatever scientific work.
c) The "academic value" of a book chapter vs a research article depends on the case and context:
1) Rene Tetzner (2021). Publishing Research as Book Chapters: Is It Worth It? 5 May 2021, Advice & Discussions on Preparing & Submitting Journal Articles for Publication, Proof-Reading Service.com Ltd., Free access: https://www.proof-reading-service.com/en/blog/publishing-research-as-book-chapters-is-it-worth-it/
In my opinion, the contents and the volume of contribution decide the value in academics. It really does not matter whether it is a research article, a review paper or book chapter.
Even though they have different nomenclature from their superficial, morphological, and semantic perspective, they converge as at formal ways of communicating ideas among scholars. Depending on the level of analysis and the type of institutions doing such analysis, they convey almost the same thing: research findings. In another narration, they can approve or disapprove theories. From another dimension, the difference lies on the type each of the mentioned scholarly outputs tries to undertake: basic, applied, action, etc. and this depends on the analysis and institutions as regard the type of problem the research is geared towards to solve.
As observed, even though I'm not saying anything rather observing the phenomena from surface without detailed and in depth analysis, each of the mentioned scholarly outputs should be regarded as a valuable contribution to the body of knowledge. This is because, knowledge is dynamic. What one takes for granted today may be of critical importance or becomes critical imperative tomorrow. In effect, even though value judgement is important, one might be good today at the expense of others and others might be better off tomorrow at the expense of that one tomorrow.
Some regard research and review articles in peer reviewed journals as more authentic and "valuable" than book chapters with respect to their academic contributions; just based on the fact that they are peer reviewed. But the assessment by the categories themselves is somewhat problematic. Publishing venues are also classified and rated by indexes, reliability and quality of the editors and publishers etc. Many factors at play. But, I believe that the authenticity, originality and rigor of the work itself should be the foremost criterion for the "value" or "merit" assessment, if necessary. As one colleague noted, citations on the work may be one criterion in this respect.