Scientific value of Letter to the Editors is less than that of original articles. The important point is that the letter type is not accepted by all journals.
Typically, the letter type has limitation in the maximum number of words used in the article or the maximum number of pages, which depend on the type of journal. A special case is Letter to the Editor, which can also be written in one page. Letter to the Editor is written to complete or criticize the contents of an original article, usually written by an expert. Usually, these articles are accepted or rejected , and journals seldom require them be revised.