each of the locations has advantages and drawbacks
boston i have a map for, and is somewhat british free, but it's overrun with religious zealots.
philadelphia i sort of have a map for, tis the largest city at the time with much invention taking place, and theres less of a british presence i think
NY is ground zero for lack of a better term as much of the city is destroyed by fire, and there will be many leftover marooned british forces fighting over the spoils. in fact it might be their only beachhead left in the new world with their fleets gone (in out time the british didnt leave till 1783).