I live in Lisbon, and here IESE has some "influence". The school is the best in Iberia, with a very strong reputation in Spain, and from what I've been talking to people in London, it has consistently increasing placement there, usually when the role requires Spanish (or if you prefer Castellano) and is linked to Iberian Business.
When I started researching for schools IESE was there on the list. Some of the reasons is that I really like the "Spanish way of life", I think that having a 2 language course is great, and for me Barcelona is the best city
. I really like Barcelona, and so does my wife.
However, if you want to go to USA, you will probably have a hard time with a degree from University of Navarra, whilst with a University of Michigan's you may have a chance in Europe. Disclaimer - that's an educated guess from someone who's living 3 years in Iberia. Of course that consulting firms hire from both Ross and IESE.
I fell that overall Ross has a stronger reputation, actually all US schools have. My boss and one of my recommender are INSEAD alumni, and both told me to go to USA schools, as they believe that MBA is an American product. I'm not telling here that Europe schools aren't good, actually their reputation are rapidly growing, but still the best professors are in USA, the best network, resources and business driven culture. On the other hand, European schools are ahead on multi-cultural issues such as language requirements, which I believe will be very important.
To make a long story short: I'd go for Ross, considering that you're primarily aim is not going to work in Barcelona or Madrid after graduation...