The 73N does about 80% JFK and 20% LGA... maybe a little less. If you want EWR and LGA, you might consider the 717 first then the M88. The 320 also flies out of EWR and LGA but not as much EWR as the 717.
If you do not want to stay in NYC, the best strategy would be to bid an airplane that is based near you.
FYI... if you work for a Delta Connection carrier and have access to DeltaNet, you can pull up all the bid packages and seniority lists and see for yourself where each aircraft flies and how senior they are.