TL;DR: There is one and only one reason to choose the Norwegian Pearl: it sails out of Boston. If you're willing to sail the same itinerary from anywhere else, sail out of New York: you'll get much newer and better ships.
But let's start at the beginning. The embarkation horror stories posted by some of the previous reviewers are clearly a thing of the past. The terminal was run in an orderly fashion. We went from ship Uber drop-off to ship in a little over an hour. The main bottleneck seemed to be that customs had not cleared the ship for boarding until sometime around noon. Until boarding could begin, all passengers were hearded into a small roped-off section of space with chairs that were almost completely full (see photo below). We had picked the 10:30-11 terminal arrival window and had to wait about 15 minutes. Perhaps if we had arrived in the terminal later, we might have waited less.
Much about the design of the Norwegian Pearl feels cumbersome and dated. The cumbersome part comes from the fact that even though the ship was filled to about half capacity (or, if you're a pessimist, half-empty), some parts still felt congested, such as the narrow corridors of Deck 7 in the evenings. On sea days, the pools, the hot tubs, and the poolside lounge chairs were completely full even with the ship at half capacity.