The two towns should actually be flip-flopped (in terms of how they are portrayed anyway).....Mattapoisett is a much more white collar enclave than Plainville is. The Roys are sort of "rough around the edges" but they are fairly successful in their businesses.
It's actually kind of interesting, not sure if this in anyway played into Michelle's issues, but Plainville is seen as sort of the "poor cousin" in the King Philip regional school system. The other 2 towns in it, Norfolk and Wrentham, are seen as the more desireable towns to live in.