Overall, the UX, but also in big part due to marketing.

Corporate/for-profit solutions tend to have enough money to pay not just for the development but the marketing of a product. Let me show you a non-social-media pair: Plex vs Jellyfin.

If you go to the individual websites, the difference is visibly stark. As a basic user with little to no understanding, which website sells the product better?

Open source most of the time can’t afford the long user experience studies and full on designer teams that make a product more likely to be chosen by the average person. Hell, open source often can’t even afford lawsuits (which is why a lot of projects go dark and disappear after accidentally stepping on the toes of someone revengeful or looking for a quick payout)… in fact most open source software is solely driven by unpaid contributors. And while there’s tradition in software engineering to contribute to open source, the same doesn’t really apply for designers.

And that brings us to UX, the most coveted topic of software engineering. Why? Because it’s not always intuitive what the users will find intuitive. After all we’re engineers, we care about the raw information, not its presentation. Sure a tidied up Excel spreadsheet looks nice, but it isn’t more functional in an overwhelming majority of the cases, than a no frills, just data spreadsheet.

That’s why most open source software feels so barebones. They’re full of features but those aren’t fancy, they’re not a nice experience for the users but simply fulfill a singular purpose.

And that to date differentiates Plex and Jellyfin, as well as any other pairing of paid-for vs open-and-free software.