I find that the type of application, open-source or proprietary, doesn't really matter from a practical use perspective. It's all about the users and the knowledge they have. In the company where I work we now exclusively run Linux servers and open-source server software. This requires a certain amount of knowledge for it to work, and because we have that our Linux-based platform blows a similar Windows-based one out of the water, and at a fraction of the cost. If our technicians had been less knowledgable and/or Windows oriented, the tables would likely have been turned. Although, having worked with enterprise setups on both platforms, I prefer Linux.
It can often be difficult to evaluate software as being "better" since it all depends on how effectively it is used, which is directly related to the amount of knowledge the user has. Assuming, of course, the software isn't severely impaired by bugs, a terrible user interface, or something else.