I don't know anything about the pfaff..but i have the 6600P, and i love her..i would not trade or sell her ever.
even if i won a top end bernina or pfaff,i would still stick with the 6600. go and join a message board that deals with each machine, and see what people think of thier machines.
ther is a message board i belong to :
http://groups.yahoo.com/group/Janome6500/
i am sure the other machine has a board aslo..