First of all Masters (if not MBA) does not guarantee you an associate position.
Second, it depends very much on a country, particular office, and 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). In this case, the competition among BAs applicants was much tougher than among associates.
- MBA hiring is different for different schools. For example, in Stanford and Harvard, you can meet many people with 2-3 MBB offers, while its 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.
To sum up - you should never expect that your interview will be easier for any reason and you should do your best to prepare.