A Pfaff for $100 is hard to beat if it lives up to your expectations in the test drive. Maybe the seller was pretty fond of it to change her mind --that's a good thing. You don't have to buy the cabinet; you might even get her to shave off $20 if you don't "need" it and it would be an ugly bear to haul in and out of your basement apartment when you move.
The Singer is beautiful, as is the cabinet, but it's too pricey, IMO. (Granted, things in BC are a lot more than things down here near DC, but they aren't hard to come by, are they, up there?) If it were me, I'd take the more practical one now (Pfaff) and save the pretty one as a reward for finishing school!