UFC definitely has the deepest talent pool. Just look at how stacked the Bantamweight, Lightweight, Middleweight and Welterweight divisions are. The preliminaries are genuinely worth watching, no other MMA organisation I believe comes to that level.
However, the pay is stupid low. How are Usman and Masvidal getting 500k for 1million PPV buys while Dillian whyte gets 3 million for 300k Buys. It doesnt make sense. The low quality gloves are also a problem, theres nothing like watching your favourite fighter go down in a fight their winning because of an eye poke...
ONE is definitely the best for the most innovative. The no weight cut rule set should be followed by all MMA organisations, we saw how Costa and Vettori fought when they didnt have to. Stronger chins, more stamina and higher power. We could get a lot more amazing fights in the UFC if they implemented that in. The new mixed rules bout is also interesting and though I dont think thatll be common place anytime soon, its still something different.