It depends on the competitive situation in a particular office, your role and the demand on the market and even your school. In general, I would not expect BA interviews to be easier than Associate interviews.
I've seen many times a situation when BAs were overprepared (case clubs very popular among students), while experienced hires were underprepared (lack of time and information about consulting interviews) and both passed
MBA hiring expectations are also different for different schools. For example, in Stanford and Harvard, you can meet many people with 2-3 MBB offers, while it's not the case in other business schools. I also can't say that people doing MBA have lots of time to prepare. I believe that brand matters and they hire more people in top schools in general.
I would also copy a list of critical things here from a similar thread:
- Not listening to the interviewer (Forgetting the information provided, not listening to the interviewer's tips, answering the wrong question)
- Poor structure (not enough levels, not seeing the big picture, a structure not answering the question / answering a wrong question)
- Using "book structures" (3c, 4p, etc) or structures not tailored enough for the case
- The candidate is not structured enough (you are structuring in the beginning, but fail to structure during the case)
- Math mistakes (one may be ok, more than 1 - no go)
- Not communicating the math properly (you don't communicate the way you do calculations and stay silent)
- Lack of creativity (candidate cannot brainstorm creatively on solving the problem)
- Lack of top-down communication (candidate does not apply the pyramid principle in his communication)
- lack of business judgment (candidates ideas are too general / do not reflect the specifics of the industry / function)
- Can the candidate talk to the client right now?
- The candidate does not look mature (outfit, behavior, language)
- The candidate is too nervous (Being a bit is ok, shaking is probably too much)
- Candidate can not provide the examples of certain traits (e.g. leadership).
- Candidate fails to answer additional questions about his stories (i.e. the story was made up)
- The candidate is not friendly / enthusiastic / shows no emotions
- The candidate stories do not differentiate from the others (e.g. Leading a team in a case competition as a lead story)