The Saladin was a survey ship with decent tactical, and it didn't see an especially large order size. The only ships with really standout orders are the Newton, which was built en-masse as a generalist cruiser for tactical and engineering use, and the Archer, which is the single most successful ship in the history of Starfleet. Starfleet loves logistics.
Besides, if you build a large ship that goes out to the frontier with a bunch of science equipment and some engineering for sustain, you've just built an explorer, and it's going to be big enough that you might as well buy the weapons and shields too.
EDIT: It also seems like we're more or less deciding between building a giant newton or a heavily armed archer here. Shuttles will steer us towards response, which means we'll be doing the Newton thing, whereas cargo will steer us towards an engineering focus.