It really comes down to preference.  The Spanish style will have a smokier flavor but since it's already cooked through, it may be a bit more crumbly when cooked.  Fresh Chorizo in the Mexican style is how I came to know this dish and it's the one I usually reach for.  I especially love the flavor that comes from the oil drippings of a good quality chorizo with the proper amount of fat content.  Mexican Chorizo tacos have just the right amount of oil to deliver the maximum flavor value in every bite.