Due to the fact that many profit oriented companies are not ready to pay the costs of publication download for their co-workers and (sadly) many governements just want good results form the researchers in their country without providing support for their universities and academic research institutions (and not only in poor countries) to have free access to major scientific databases, several scientits either use sci-hub or just cite papers that are freely available on the internet (legally or illegally). I am fully aware of the costs of high quality publishing (being a co-worker of an online journal) and of the fact that someone has to pay the costs: either the readers or the authors. (It is another question that scientific publication, as well as conference organization gradually became a dirty money collecting business). Nevertheless, my impression is that open access publications (I mean really peer reviewed, high quality open access journal, not the predatory ones) have some advantage, insofar as they are available for "poor" researcher, therefore sometimes are better cited. I have so statistics to support this opinion, it is just a feeling.