gmijaresshafai
The JD/MBA is my personal preference; my short and long term goals will utilize both and I know I will appreciate the different education.
I think you just answered your own question. The only "downside" to the JD/MBA is that it's so compressed and you spend most of your time at the law school, it's not your typical MBA experience, but it sounds like law is your priority, so that would make the JD/MBA appropriate.
You might be the first person in the history of man to turn down HBS for Kellogg, but these sound like good reasons to do so:
1) Northwestern's Law is stronger than Emory
2) Three years vice five years
On the other hand, going to HBS would give you the full MBA experience from the most recognized brand on the planet and keep your options open - you may find that you don't want to go to law school afterwards when you see the recruiting opportunities available at B-school.
Best of luck to you!