There's really only one reason why NY was renewed and Miami was axed
I think the fact that NY is the younger show, it would've been cheaper to produce. I'm glad it was renewed, but I have to say that Miami should've been renewed cause the ratings were higher. But I also must point out another reason I think Miami was axed:
The fact that it aired on Sundays made it difficult because football games in the fall were pushing it back later so they could finish.
I prefer Mac Taylor and his team over Horatio Caine and his team however, so I was actually hoping NY would be renewed. Can't wait for next season!