Choosing MBAs are a tricky business. You need to be very clear on what your objectives and constraints are. Some people look at costs, GMAT scores, rankings or the opportunities.
For INSEAD, it's the people that you are rubbing shoulders with that will open the doors for you. Very few people can afford to pay the $100k school fees so you know you are with the "elite".
The top schools have very good connections with the corporate world and that helps to provide job or internships opportunities with the best companies around.
Lastly, rankings (or brand) are important because at the end of the day you will graduate with an MBA. It's the name of the school that sets you apart from the rest of the candidates.
Just my 2 cents worth