Hi Julia
I'm a real estate agent and investor in both NJ and NY, so this hits home for me.
Lot's of aspects to cover such as the goal and how much you want/are comfortable with managing. My partners and I see NYC downtrending in many higher income areas as far as appreciation goes. NJ is booming, some areas have increased as much as 10-15% in appreciation over the past couple years so thats massive (not to mention the rents are through the roof as well).
For this reason, I also agree NJ is the way to go. As Darren said, Newark (and similar areas such as East Orange etc..) might be a bit of a challenge for a newer investor. However, I wouldn't let that stop you without at least looking into the area(s) firsthand with someone experienced in those locations. Most of the tenant issues I've experienced or have seen could have been mitigated with proper tenant screening and a solid lease agreement. The way I see it is: more time invested = more potential profit. Less time invested and more comfort = less potential profit.
There are plenty of areas to look at so I would suggest doing a tour of the area and go from there. Bergen, Essex, Hudson, Passaic, and Union County are going to be your preferred choices given the distance criteria you supplied.