88: large category with fast seniority advancement, but the hardest working of the three.
320: much smaller category and fewer trips and slower advancement. large percentage of one or both day non commutable trips due to the nature of NYC domestic coupled with a small category that was created way sooner than it needed to be for the sole purpose of making pilots eat the cost of as many NYC overnights as possible. despite it being one of the worst categories in the system for the bottom 50%, people senior to you will continuously be bidding in as there's just something mysteriously alluring about people wanting to say they're on "the bus in new york".
737: fairly large category, massive trip variety but the slowest advancement of the three.

I'd pick either the 88 for pure advancement/seniority or the 737 for broader over all choices. Either way you'll be in one of, if not the, easiest commutes in the system with the half hourly flight schedules and near always seat or jumpseat availability.

Of the three you can't go wrong though.