The thing I like to avoid most is when the issue boils down to either:
Someone arguing your're a bad person for not releasing your source. It's unethical. You should be ashamed.
And the other way around some critiques on Open Source projects come across way too ungrateful
and disparaging and blind towards the accomplishments and benefits they do bring to the table.
Besides that though, there are plenty of valid critiques on when proprietary products fail for various reasons.
As much as you can argue cases in which open source projects aren't quite where they need to be for serious consideration.
It can also be discussed if there may be even a causal relationship to these problems by virtue of the development paradigm.
Some might say, there is no downside to this or that. It's better on principle, it's just that people are not enlightened enough to take more advantage of it.
I believe that software development is a problem that exceeds pure technical consideration, because in the end the coders are just humans too.
So there is all kinds of questions about psychology, culture, motivations, economics, the situation, etc, that I think are important to factor in.
I think that there are at least associative relationships between these further factors and the development paradigms, that make the issue very complex.
As an example, I believe that a person's motivation is the most important key to the success.
We can then look at factors of motivation, and how powerful their psychological effect is.
Imagine that working on a snippet of code means, you are fully responsible for it, so far that you are held fully accountable for it. If the product succeeds because of your code, you may get a promotion and a higher income. If it fails because of you, you may lose your job, all your money. You may even go to jail in some cases. The company may sink, with all your colleages and friends. So you are sitting there, and maybe you give your code a couple more looks. Make a couple more test runs. Maybe listen more to customer complains. Maybe you even feel a greater sense of duty to do work that's not always fun and rewarding. The stakes are high, and your name is on it. So one person, from motivation to qualification, may put more value into a work than a hundred hobbyists.
Now I don't want to make the issue too simple. Because in a different scenario, that employee might be underpayed and frustrated with the job, feel like a cog with no say, etc, which also is bad for motivation. And in a project as a free hobby, you might be motivated because you just love to play with it and interacting with other creatives, and feel responsible for it as it grows on you.
Then we can argue about the difference of these as either a fully integrated development paradigm, or a mere fact of having companies release their sources. But there are such a huge amount of consequences to that too, what this means for companies and investors, one might not appreciate at first either. Then the discussion is at danger into devolving into fundamental critiques on society and life itself, it can get pretty awkward.
