I already put my stuff in another repository (e.g. arXiv ). Why should I put it in QSpace?
QSpace will give your paper a URL that will never break – in 20 years and beyond, a citation to your paper that gives the QSpace link will still work and get people to your paper.
Also, you don’t need to worry that the server will be maintained. Sometimes, at the departmental level, the “care and feeding” of a project or server is dependent on a set of interested individuals, and if they leave or get new interests, the project may languish. A fundamental role of libraries is to develop and maintain collections.
We don’t know the capabilities of your eprint server, but QSpace provides “access control” – if you don’t happen to want the whole world to see something, we can control access to it, that is, the people you want to see your paper will be asked to log in to see it.