Hi,
I really don't get it why so many people are name obsessed in terms of general reputation of a business school and why such distinction between MBA in France/Europe for career in Europe or American MBA for career in the USA, Japan, Asia and etc.
Both HEC and Essec are great schools both highly ranked in Europe, HEC internationally, and although business people may not have heard of them (just as well as they may not have heard of some top American business schools), human resource managers, if they are good, should know both HEC and Essec whether they are in Europe or Asia or America.
Just because you want a career in Europe or in America does not mean that you should target European or American MBA for respective markets. Most big top international companies are either American or European anyway. Not everyone who works for top companies in America has obtained MBA from American business school. Companies employ you for your knowledge and capabilities on top of your choice of business school. I know bunch of people who moved to America for work and they work for top American firms with their European MBAs or other masters programs from schools ranked lower then LBS or LSE or HEC and etc.
Don't let anyone discourage you from your choice of school simply because someone may have not heard of it. We don't count, recruitment managers count and they all, I am sure, know HEC and Essec.
Go for it and good luck