I am not sure about the writing skills but for the first time, surely writing a chapter in an edited book will enhance your research aptitude and relevant skills. A lot of things depend on the editor. He/she will guide you and if this guidance is a high-quality one, so I can easily assume that the whole process will be highly beneficial.
Writing a chapter in an edited book has all the positive recognition of a scholarly piece. It can stand out as a contribution to the discipline and not just an enhancement of writing skill or research aptitude. Besides their books, articles and other contributions, scholars often list their book chapter(s) in their resume as contribution to the literature. I remember when an author won the Nobel Prize, he asked us to reuse a chapter he had contributed in a book I co-edit as part of his achievement. So please do make such writing, research and academic contributions.