I think where there is water there are fish! If you learn the water and the habitat, you will increase your chances of catching. Whether that habitat is the Raritan, IBSP, Cape May, etc...if you get familiar with it and get to know where fish hold, when and what they are feeding on and their many other habits, you will catch fish. As long as you have access to these areas you have a chance to catch fish.
I think at any given time, someone is catching fish in the Raritan and in IBSP equally, especially from shore. If you were talking about where to dock or put a boat in...I would say the Raritan area because there is just more opportunity. However, from shore, I think you have just as much access and just as much structure. You are talking about 2 different types of water, though. Each one has it's time or times to be fished and will hold fish at different times of the years.
So, IMO, if you want to catch a fish, just go fishing...as much as you can. The more you fish, the more you have a better chance of catching.