Hey! Congrats on your admits!
For the easy question about the GMAT - For a Master's student, a high GMAT (and to an extent GRE score too) can help you get higher ranking programs or get scholarships at the ones you already got into, so there is a benefit... BUT only if you can get a score over 655 on the GMAT. A high GMAT score validates your accomplishments, your academic aptitude and helps drive up the School's average. Hopefully this gives you a simple answer.
About which of these to pick, I would pick the LARGET (biggest student body) as none of these provide work placement and many of the second tier programs lack ability placing into large MNC's so going to school in Spain and France would be tricky as you would not get recruited for the local firms that need language skills.
I guess it somewhat depends on what you want to do and what language you speak and where you want to recruit.