Nowadays, the interest towards electronic voting systems is increasing. However, in the existing e-voting systems several issues need to be resolved regarding usability and security. Is an e-voting system usable? Does it guarantee security? To answer these questions, we have conducted a comparative study of a non-exhaustive list of e-voting systems with a focus on usability and security properties. We have first identified the main tasks of an e-voting system and the usability and security properties that must be provided by a e-voting system. Then, we have analyzed what are the different tasks and usability and security properties provided by the selected e-voting systems and how they have been implemented, as well as their impact on the functioning of the system. Our study highlighted the strong relationship between security and usability. More specifically, we came to the conclusion that even if a system fulfills many security properties, its security can be fully guaranteed if it is usable. Finding the good tradeoff between security and usability increases the confidence of the users in these systems, which is an essential parameter.