My advice is to stay away from Bernette. Those machines are NOT traditional Bernina quality. It has been many years since I worked in a sewing machine dealerships, but at that time the Bernette machines were (in my personal opinion) junk. Even if they have improved since then, I'm sure there are better quality machines out there.
Pfaff has a great reputation. Without knowing anything more about the machines you are comparing, I would definitely go with the Pfaff.