It has been discussed in RG many times. It is always preferable to publish in journals because they are indexed through various sources and thus have more chance of citation.
However, if a book is published after adequate review by good publishers, chapters can also considered as good contributions.
Peer-reviewed research journal is the first best option. If cannot get accepted in research journals after a try or two, chapter is a second tier option.
The choice belongs to the author. In my opinion, the article is more autonomous and the chapter is more collective. I believe the article is broader and easier to disclose while the chapter is always tied to a "scientific package."
Dear Dr Mahmoud El-Mezayen, Many scholar has already asked similar questions and well discussed here. Generally, article published in a well indexted journal has better dissemination and good citations too.
Both are essential for an academic author. As an academic author, it will be nice when you look at your publication list to see research articles, review articles, book chapters, editorials/commentaries, case study or research communications including books/monographs, books edited etc. All of the above have their own style/structure which will be a good experience in guiding others.
In terms of citation, visibility, and pace of publishing, I think a journal article should be favored.
Writing a chapter is much difficult. Any good researcher can write an article, but to write a chapter you need a life of teaching and working in research to write a chapter.
In addition, sometimes you need to read a chapter to understand some methods in physics. one article is not enough.
I wrote some manuscripts of books in Arabic on physics, never could be satisfied to do publish them, but I used some chapters of them to teach the oriented physics for the branches of science, medicine and engineering students.
I really wanted to be more comfortable with writing research articles, as I have been requested to share in writing books with other authors last weeks. It is a good idea but it is time consuming at least for me at this moment.
An academic should have a portfolio of academic writings including journal articles, proceedings, books, chapters in books etc. However, more importance is attached to peer-reviewed journal publications due to factors like increased visibility and impact. Moreover, in my Institution, articles in reputable journals are rated higher than book chapters during promotion