Thanks for the comments and suggestions.
I think I am even more confused now since you have recommended most of the resorts in North America
From what you say I am leaning towards Vail or Whistler. Alta looks good to but getting there from Spain may be more difficult.
Although I can get a cheap flights ($600 to Denver, for example), the rest of the costs are significantly higher than in Europe (especially lifts and lodging). I will now check with the rest of the group and see if we consider it or not.
Thanks!!!