I have two Pfaff's and love them. I love the IDT ( built in dual feed). They run and run - are real work horses. They are quiet and well manufactured. My dad was an engineer and mechanic and always said a good machine of any kind, ran quiet and smoothly whether it was a car, washing machine or sewing machine.
But they are pricey -- but I feel worth it.
However, I feel the best thing to do is to buy a quality machine from a local, reputable dealer that has a service person on board. Pfaff, Viking, Bernina, Baby Lock, Janome, Suki, etc are all great. but if something happens and you have to send it away and wait a long time - it is not worth it.