I enjoy OneFC. Some good fighters, a lot of good fights, and overall feels polished and professional. They also have their own unique vibe. They are currently the best non-UFC org by far imo.
Bellator can sometimes be really, really good, but it's when I expect the best from them that I am disappointed with how lame they usually are.
Rizin, the few times I've seen it, is enjoyable, with extremely questionable match-making, a huge inconsistency in terms of fight quality, and sometimes being just a step above fight circus. But their cards are always interesting and I always enjoy them, even if it is sometimes a guilty pleasure.
PFL is like Bellator, if Bellator were the UFC.
The UFC has a lot of really good fights, even on the prelims. The production is professional, but unimaginative and unartistic. Their announcers are almost always hot garbage. I'm looking at you DC.