I have both the older regional series and the newer northeast series, and there is a way to open data from one series into the other. If they are both installed in your computer, you open one into say the northeast CD, and then merge in the tracks or waypoints from the NYC CD.
I also have Terrain Navigator from Maptech and each program has its good points and bad points. I find it easier to create and store customized maps in TOPO, on the other hand, I find the map printed out on Terrain Navigator is clearer, especially when magnified. There is a new version called Terrain Navigator Pro that we are using in Search and Rescue management, which is clearly superior, but much more expensive. One thing TOPO can still do that is better is automatically print out maps that tile together, when you want a map bigger than your printer capacity.
One thing that I have found, that frankly surprised me, is that neither program has the latest versions of the USGS quads that were put out in the 1990s. We were doing searches in newly developed regions in New Jersey and our newer USGS maps showed more of the new roads and construction, than either of our digital mapping programs. Neither of these programs show the new part of I-287 in NJ for example, which has been around for 12 years, but almost all of the USGS quads do, with the exception of Sloatsburg, NY, which has not been updated.