I do realize that they are within a few miles of each other. That said, I also realize having actually lived in boston that my professors who made a very distinct point about the different demographics they serve had a point made after years within the school that was more valid.
I do agree that they are competing for best faculty, staff, and students. But I don't believe that they are competing for patients because as you pointed out there are enough to go around and as I pointed out the demographics in chinatown side vs. that in BMC vs. that near Harvard hospitals is different.
This is evident from everyone I've ever talked to in BMC who has done either medical or dental related training or teaching there.
Furthermore, the point about being in competition for faculty, staff, etc. is also true amongst schools in different cities in a given state
So just cuz SUNY downstate is isolated from AECOM in the bronx and Columbia and Cornell in Manhattan doesn't mean that all the NY schools aren't competing with each other for faculty, staff, and students as well.
So that point is kind of moot point.
But that said, based on the bigger city aspect of NYC and diversity of Brooklyn especially, I'd imagine Downstate has a good clinical experience. And that point of your original post I agree with completely.