Why use a professional English-language editor?
Put simply, it will increase your chances of publication and, once published, your citation count.
Studies show that the acceptance rate of manuscripts is inversely proportional to the number of writing errors it contains. No matter how good the science is, the chances of acceptance of a manuscript for publication decline substantially if the writing is confusing, illogical, or incorrect. Simply browse through a few common journals on the web and you will find plenty of evidence of this fact. Consider the following statements from leading scientific journals:
Applied Physics Letters: Papers that are judged to be below the standards for APL will be returned to the authors for rewriting and can be rejected for the language reason alone. Such problems may be avoided and publication expedited if the manuscript is edited by a professional English-language editing service before the initial submission.
Journal of the American Chemical Society: Any author who is not fully fluent in idiomatic English is urged to obtain assistance with manuscript preparation from a professional editing service. Manuscripts with grammar or language usage deficiencies are handicapped during the scientific review process and may be returned to the author for rewriting before peer review or before acceptance.
Materials Research Bulletin: It is essential that the manuscript is written in clear and fluent English. Papers written in poor English are subject to rejection without review
Pure and Applied Chemistry (Editor): I strongly recommend that you consult a technically informed language expert who is sufficiently familiar with the topic, to read the revision for overall comprehension, and to ensure that no scientifically misleading statements are present.
Physical Review and Physical Review Letters: If your native language is not English, please consider enlisting the help of an English-speaking editor in preparing the text.
Furthermore, poorly written articles do not receive the citations that their science may deserve for the very simple reason that scientists do not read, and therefore do not cite, articles that they find incomprehensible. As any researcher knows, a lack of citations can have a significant impact on a career. In a virtuous cycle, highly cited articles open the door to high-impact journals, more grant money, better facilities, more research, etc.
Thus, the manner in which data are communicated is nearly as important as the scientific results themselves, so be sure to demand the best from the editing service that you use.