As a researcher you have a variety of options for sharing your work online. At the end of the day the most important question is usually "How are interested readers going to find my work?". The video above will provide you an overview of the strengths, weaknesses and connections between these platforms. To summarize some key points:
(1) Institutional Repositories: Enable institutions like the University of Windsor (Scholarship at UWindsor) to provide open access, preservation and showcase their research. By design they are optimized for indexing in major academic search engines like Google Scholar and integrated in research networks like openDOAR. This allows readers to seamlessly discover content from a wide variety of institions with simply click of a PDF download link. Also can have there content harvested by disciplinary collections (see 2).
(2) Disciplinary Repositories: Collect research along disciplinary lines. For example, ArXiv, SSRN, PhilPapers, PubMed. May provide discipline specific discovery tools.
(3) Commercial Academic Social Platforms: Collect research across institutional and disciplinlary lines. Sites like Academia.edu and Research Gate are useful options for authors looking to share their work and connect with other researchers. As commercial products the commitment to preservation of content is less clear. Not actually open access as they require account creation for users to access the metadata and full-text. Not a long term solution to preservation and access to content, but a strong social platform form sharing.
It can be helpful to leverage all of these mediums to communicate about your work. The network of Institutional repositories like Scholarship at UWindsor provide a stable backbone of open access research that can be shared across a variety of platforms.
For me information visit: http://leddy.uwindsor.ca/open-access