Although, through force of habit, we all think 660 has a better signal in the NY market, with the possible exception of Eastern Suffolk County on Long Island, the 101.9 signal is cleaner and clearer day and night in the NY Radio Market Counties that matter for the day-to-day ratings and ad sales. Drive around and A-B the two signals for yourselves. Depending on location, 660 can have electrical interference problems that 101.9 doesn't have.
Remember, Westchester, Rockland, and Putnam counties are the only Hudson Valley counties that matter. In Jersey, Sussex, Warren, Ocean, Mercer and Hunterdon, are all outside the market that counts. And in Connecticut only a small part of Fairfield County matters in the ratings. So, 101.9 has the better signal in the market, for ratings driven day-to-day sales, and it probably offers better demos too.
On the other hand, 660 has a massive long distance signal, especially at night, and therefore would work much better for a national network trying to attract a national audience, even if that out-of-market audience doesn't count in the ratings, the coverage will help build the national brand.
And when it comes to game coverage, even though the Yankees are on a similar massive AM signal, from the same tower, they still have affiliate stations in adjacent markets to serve those fans who still live close enough to go to the stadium for games. And the Jets and Giants have similar adjacent market arrangements.
The most likely scenario is that 660 goes mostly national, 101.9 talks local, and both stations are available for major sports team games like the Yankees, Mets, and Giants. Basketball and Hockey can, probably, more than adequately cover their fan base on FM, and can arrange for adjacent market affiliates if they think it necessary.
But when it comes to ratings and sales for day-to-day sports talk within the defined Arbitron market, the FM signal is the more important one, and if it isn't today, it, undoubtedly, will be very soon.