I love BB because he simply doesn't let himself be swayed by things like honor or stains on his reputation. He acts rationally most of the time and only takes risks if it's worth it. However, the other emperors are also very intelligent and act strategically and rationally, especially in the way they manage their empires. There's no dumb Yonkou.
I understand the preference for BB because he was a character we saw grow from nothing to where he is today, and he was very cunning and intelligent along the way. While the others were already entrenched in the position he now holds, we didn't see much of what Kaido and Big Mom did to become Yonkou, but we saw firsthand BB doing it.
Blackbeard isn't necessarily a bad villain. I mean, risking a war against Kaido or Big Mom, even if he were to win, would result in heavy losses. This was one of the reasons even Whitebeard, who is on par with Roger, avoided fighting Kaido in Wano. He would win the war and immediately be targeted by Shanks. The reason Shanks was in Wano was for a possible attempt by Blackbeard vs Straw Hat recovering, with reduced numbers, etc. Blackbeard did the right thing in going after Law.
No one was crazy enough to risk a war in Wano with Kaido, not even the prime Whitebeard. Luffy did so with alliances and his crew, but he didn't even use his grand fleet; most of the forces he gathered were internally from Wano itself. The Yonkous live in a stalemate; any widespread battle between them opens up a huge gap for possible interventions from other enemies. The Marines were literally waiting for the end of the fight between Kaido and Big Mom so they could act. Things aren't as simple as people think.