The best reason to look at Brooklyn and Hoboken (and Astoria for that matter) is cost vs Manhattan. I’d also suggest looking at Brooklyn because you get a different feel for NY. Brooklyn (at least parts like Park Slope, Williamsburg, Greenpoint and Brooklyn Heights) and Astoria have a vibrant culture of their own comparable to the City and are within easy reach of Manhattan tourist and night spots by subway. And let’s face it, if you live in Manhattan, you automatically become a snob and won’t go to Brooklyn or Queens unless you have to.