Aren't all the other ones you mention closed source as well? Like Kraken and SourceTree for sure.
Fork is made by one person.
Not making any assumptions here, but if you're evaluating risks around compromises in one of the two products, I think Fork is higher risk.
The business model of Fork is unknown, so to me it's a clear no-no. Can't afford to put a tool in my workflow not knowing if in a few months it will become yet another service I must subscribe to