Ashish - it depends but, generally, the journal article will 'trump' the book chapter. It also depends on what you mean by 'weightage'. If you mean Impact Factor - then book chapters are not assigned Impact Factors. If you mean citation - both count. Some of my highest citation is from a multi-edition and successful Nursing & Midwifery Research book that I co-edit/author. That said, be aware that (say in Google Scholar) the citation is attributed to the book - and not individual book chapters. With ResearchGate - it is both the book and book chapters.

What is probably best to consider, is 'what does your institution and/or majority of institutions in your country identify with - for career progression etc?' In most institutions I have worked in - book chapters are scored lower than journal articles. That said - I would still argue that a book chapter in a well-established and highly cited book is better, overall, than a journal article in a low-ranked, low cited journal.

This is not easy. There are open-access journals that are lousy, and there are books that are very prestigious to be associated with, through a chapter. But if we just take a rough average, I would say that the journal article trumps the chapter. In salary discussions, for example, I bet that journal papers are counted, but not chapters or proceedings. By the way, in some fields, proceedings papers are more prestigious than journal articles!

Yes, it's a jungle out there, and the best approach is just to go about your business, without jumping on every opportunity. The most basic advise is to go for journal papers. But I may be biased because I am a mathematician. :-)