There is a significant difference in job propects between these schools.
Considering how expensive they all are, $20K is a pretty negligible difference. I would go to Columbia/NYU if it becomes an option, even if you want to be in DC eventually.
If you want public/interest govt, I've heard that NYU has one of the best LRAP programs out there. As for big firm jobs: the OCI deadlines may have passed at these schools already. If so, getting a big firm job is going to be tough. Also consider that the economy is in the toilet right now and big firm hiring has been seriously curtailed compared to what it was in past years.