My husband was born and raised in NMB when it was much more peaceful, secure, clean, neat mostly Jewish and Italian neighborhood. I used to walk in the evenings out there with him in the earlyh 80's without a qualm, and it was even quieter in his youth.
Now, yeah, crime is way up. Gangs. A more run-down appearance to large areas of it. As the poster above said, pockets of it are still nice. Saying it's like Queens is not actually a bady way to put it.

Our part of it (near City Hall not too far from Aventura) has started to look a bit faded. Owners not keeping up lawns/shrubbery, putting off painting and roof repairs. It's a bit sad. We're pretty "multicultural" with various minorities (Asian, Hispanic, Caribbean) and religions (Christian, Jewish, Muslim, Hindu).
The parts closer to Aventura and Ives are nicer. Down 163rd street, where back in the 80's the mall was THE hang-out, is now one where you keep hearing about crime--store hold-ups, car break-ins, etc.
It all depends where you stay, what part.
I'm thinking if your choice is between NMB and Kendall, Kendall might be a better idea if you worry a lot about crime. If you want to be closer to the beaches and to a Jewish area (Aventura and parts of NMB have a strong Jewish presence and kosher restaurants, including Kosher Chinese and terrific Kosher pizza at Jerusalem Pizza on 163rd and, um, around 8th avenue, I forget exactly.)
Best of luck wherever you hang your hat...
M.