I agree with most of the comments. First, figure out what you are going to be using it for. Second, are you familiar with machines and won't need any help getting started? Third, is there any warranty on the Craig's List machines, Fourth, with every kind of machine, there can be lemons. You'd get service at a dealer, whereas you wouldn't from an individual. Fifth, there are always deals out there. I don't think either one is a REALLY good deal for used machines.
I have a 7570 pfaff, a 2170 Pfaff and a new 830 Bernina. I use each of them for different things and I have had good luck with them all. However, I am partial to the Bernina because of the way it is built and the LARGE harp. Good luck and let us know what you decide.