The extensibility and transparency has always been the big ones for me. It is such a pain not being able to dig into exactly how a program works. Documentation is ok but open code is infinitely better.
I've been a fan of FOSS for a while, but the big thing pushing me even further is the fact that commercial services are adding so much advertising and data tracking. I'd happily pay for a piece of software that works as promised and does not include advertising, but when you start throwing ads in my face or putting features behind "IAPs" and subscriptions, I'm going to look for alternatives.
Great post!
I've often used low cost as an argument for choosing open source software in my [IRL] communities, as the other advantages aren't that successful when talking to people on a personal level.
This post elaborates on those other advantages in a convincing way.
I've described it as cost flexible, because you should be funding or ensure developers are funded to a level appropriate level of risk to operations if a vulnerability is discovered or a critical failure prevents a correct operation.
That's for big business and governments at least. Small businesses also has the same concerns but the risk matrix for them is just different.
It's also good to think of other differentiators because pretty much every business offers financial incentives to win an initial contract if it means recurring revenue.