PVD's cachement area also includes eastern CT (Groton/New London, Putnam, etc.) which houses 2 huge Casinos, all of which add to our draw. Most of Cape Cod will use PVD as it easier to get to (most of the time) than BOS as well. The SW BOS suburbs might be "pooper," but RI versus NH isn't close. RI has a very large military presesnce (5th most used commercial airport for the military in the U.S.), a large and growing pharmaceutical industry (coporate HQ for CVS and Brooks' pharmacies and Amgen's main drug manufacturing/support center for Enbrel), large banking and invetment company presence (Fidelity, Citizens Bank HQ, Bank of America, and Bank RI), and numerous other major companies (Textron World HQ - owns Cessna aviation anoung many other companies, Hasbro Toys HQ, Paul Arpin Van Lines, Amtrol - makes water tanks, GTech - huge lottery machine and sytems maker/supporter, General Dynamics - makes nuclear subs for the Navy, Toray Plastics, and many more). RI's higher education centers are also a bit more robust than NH with Brown (Ivy League $$$) Providence College, Bryant University, RI School of Design (often ranked just behind Juliard for performing arts), Johnson & Wales Univ (highly regarding for services industry programs and cooking), Salve Regina (good business program), Roger Williams, URI (great engineering school and marine biology), with several other smaller specialized schools as well. Most shoreline cities and towns in RI are filled with very highly paid doctors, lawyers, and business owners which drives up RI's average income (many of these folks work in the BOS area). Not to mention places like Newport and Barrington, which are known as "rich people towns." Without actually knowing the average income of NH and RI, I'd be willing to bet RI's is at least a little higher (absolutely nothing against NH, by the way!).
An issue with MHT's cachement area is that is a "half circle." All the draw comes from the southern quardrants (the north is mostly trees, mountains, and farms). PVD draws from all directions (somewhere around 3 million people within an hour's drive).