As far as I know, the information you've got about Minsheng is accurate. All I can tell you for certain is that the payscale for BAA is correct, but the other information matches what I've heard about Minsheng. So yes, the Minsheng contract is miles ahead of BAA's in virtually every respect. The possibility of improvement at BAA should not be ruled out, but since the merger was announced, there has been not so much as a hint that BAA's contract will be brought up to par with Minsheng.
I heard through one of the recruiting agencies very recently that a pilot did the interview, medical and screening for Minsheng, and was then offered an inferior contract with BAA on the same aircraft. I didn't hear if he accepted the offer, but he was understandably confused. He had specifically chosen to screen for Minsheng instead of BAA for the aforementioned reasons.
One thing we do know is that the plan is to keep BAA and Minsheng operations seperate, and for the current management to remain in place. If a pilot were to come to BAA right now, they would be employed by BAA, on a BAA contract, and their CAAC license would be held by BAA. I could not recommend signing a BAA contract with the expectation that it will be amended to equal that of Minsheng.