I would make the trip to the f/s in Farmington CT (about 40 minutes from springfield at the westfarms mall
Westfarms) before I'd make the nearly 1h 30m+ drive from northampton to wrentam. Of course, you won't get 30 percent off at the f/s. The only complaint I have about the westfarms is that I found the MAs to not be the friendliest. I believe there are also 2 or 3 counters at westfarms.
I'm in west-central NH, and tend to go the f/s in Burlington, MA. I go to Wrentham once and a while when I'm visiting family in southern MA, but more often than not I don't even bother stopping there.
On another note, you can go to the CCO in Clinton, CT and stop at westfarms on the way there or back. Northampton to Clinton is mapquesting at about 6 minutes closer than Wrentham, plus you'll pass a f/s on the way: win/win.
Clinton Crossing Premium Outlets Clinton Crossing is managed/owned by the same company as Wrentham (Chelsea Premium Outlets.)