I would argue that there are many reasons as to why Open Source is a better solution for developing Software and I think that those are both Technical as well as Philosophical.
I won't go into details as to the differences between the concept of Free Software and Open Source Software for I believe that the real world implications are fundamentally more important than the philosophical background as Philosophy should be a mean to critice the world in a positive manner.
(From now on I will refer to both as one concept)

The objective that we, as Humanity, should strive for is to better the lives of everyone in an ethical way and one such, although less important than the economic system, direction I think we should take is that of Open Source.

The key to understanding the advantages of Open Source is that of comprehending the relations between a Positive Liberty and a Negative One for I would argue that Liberty is not intrinsically positive whereby it realises something that is objectively damaging both individually as well as systemically.
In the case of Open Source however the liberty of running the software for whichever reason one might have as well as being able to modify that software and redistribute it freely including such modifications is absolutely positive.
One might argue that security could be harder to maintain in Open Source Projects as the accessibility of code can help hackers breach through more easily but that can be effectively reduced by penetration testing; It also has to be noted that including any type of backdoor becomes impossible.

In Conclusion the use of Open Source has many advantages and improvements to the transparency and pace of development of any Software, especially if such development is done in a democratic and social manner.
One example that comes to mind is surely that of the Gnome Foundation.