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would open source be enough of a reason to switch?

I would rather pay for something knowing it's actively maintained and less chance of it going away.

Paying for something doesn't mean it won't go away.

In this situation the whole point of OSS is that it doesn't matter if the service "goes away" because you can self host the same software

You're right, it doesn't technically "go away", but OSS does become unmaintained and imo that makes it not worth depending on.