I think that M&A deals may potentially destroy jobs in the long run. If company A and B both have a CFO, it is likely that they will only require 1 CFO, and the other CFO will either be demoted or made redundant. This will be a good thing for the company as a means to cut costs, but on the other hand, it may mean more unhappy emoployees.
I think it is dependent on the size and the structure of the two organizations. If both are relatively small and this could be doubling their size, then I would think it would create positions to be able to handle the jump in assets. If it is a large taking another medium to large organization, you will see more jobs being dissolved due to redundancy in positions.