The most important thing you can do as you begin (or continue) your search for the next stepping stone in your career, is to start by assessing your own priorities. What is important to you? How do the firms you are considering rank on what is important to you? The list should include both professional and personal considerations because every firm is going to have a different balance. An example of such a list might be:
Once you haven this list in front of you, you can begin to compare it with what each of the firms you are considering has to offer. To make that comparison you will need to do some research. Find a connection at each of the firms that you are considering (on your own or through your recruiter) and interview that person to evaluate the firms on your criteria. Once you are armed with that background information you will be better equipped to make your decision.