You still haven't explained why B3A would be better than B2A properly.
I did say this:
Because we don't want to be fighting the Sword Saint (which is what a 2 vote seems to be leaning towards). And because if we knock both their heads and say "settle down" that's very different from knocking just Bai Jiutian's head and declaring victory for the Fire Cult. In the former case, both sides can be made to stop fighting. In the latter case, they'll be pissed and we're in for the battle and hoping for victory. At the same time, we alienate the fuck out of the Orthodox sects if we go with 2 (and we kinda like the frathouse, the Emei, Song Lingshu, etc.; Jing is strangely on good terms with a lot of Eight Sects heads despite his massive unorthodox rep).
Also, a B3 vote is most likely to be in line with what Zhang Jue wants, which is important not just because it'll make him happy down the road that we're proving our skills, but because if he does show up (as the Sword Saint is expecting) he might boss us around and/or join the fray if we he doesn't like what we're doing.
While the cultists seem to be trying to make a break for it at the present, they might just as easily try to push for victory if they see the opportunity. In that case, it's still best for us to be on our own side because it decreases the chances of the two sides wanting to defeat the other (because we'll be in the middle).
If Vahista does make a break for it with our assistance, then it could quite possibly result in Guo Fu getting killed, which is also not an outcome we want. And even if they make an escape, there is no guarantee the Eight Sects wouldn't chase them and inflict more attrition during the escape.
Our goal is to get both sides to back down from the fight, it seems. In that case, I'd rather vote B3. With our new skills, their battle-worn conditions, and our allies, it should be doable to get both sides to back down.
Then there is the fact that Murong Yandi is voting 3, and, well, bros.