I am not an expert but a quick look at the spects shows that the ‘737’ has a longer range by 350 miles and can stay on station an hour longer than the P-3.
I believe the specs, to a point ...
Turboprops are inherently more efficient at low altitudes. Perhaps the P-8 can carry a LOT more fuel, and thus has a longer patrol/loiter radius.
Perhaps new equipment and sensors will permit the P-8 to putz around at a nice fuel efficient 25,000 ft.
And perhaps the days of flying below the scud, in the rain and snow, actually LOOKING OUT THE WINDOW are over.
dunno.
Paint me anachronistic ;-)