If you're a fan of The Good Place, I'd say go with Primary Trust. Fat Ham will be performed around regional theaters for decades to come. And while Saheem Ali did great work on it, the production isn't necessarily the reason to see it. But William Jackson Harper is giving a fantastic performance in Primary Trust (for what it's worth, I also really loved the play itself - but I also love Fat Ham, so it's kind of a wash on that front).
Also, with respect to quizking, I'd be very surprised if Primary Trust moves to Broadway. The current run is selling well enough, but it was papering earlier on, and even now the demand isn't high enough to justify a transfer. Stranger things have happened, for sure, but I'd advise against banking on it.