I'll always be an Atlantic guy. I enjoy the boats better, and the lone wolf taking on an entire convoy, and the campaign going from easy to hard verses hard to "where did all the targets go?"
However any REAL subsimmer will like enjoy and be excited about either, and that is my position as well. I often find (ever since IL-2 for sure; big learning experience) that historic games like this can drive you to learn a lot more about the history. Atlantic, pacific, air sea ground, it doesn't matter. Learning more about history is always a good thing. I'll be reading up on my pacific history while I play, rest assured.