First, diversity in New Jersey typically comes in two flavors; economic or ethnic. Rarely both. You may find people of different ethnic backgrounds in both those towns, but most of them ain’t hurting, financially.

Second, Montclair and South Orange are on different rail lines so you should check the train schedules to make it works for your own schedule. South Orange is only a few stops from the city or Hoboken. Montclair has (I think) 7 stops just in town and the ride can be quick or interminable, depending on the train you catch. If you’re going to the financial district, and depending on your income level, I assume you’ll head for Hoboken over Penn Station and take either the expensive but very fast ferry, or the cheaper but longer/sardine packed PATH.

Sorry for the salty discourse. Just a grumpy old bastid.