Well, I have 5 Berninas (vintage 731 and 930, modern 440, 820, and 240) and I can't recommend them highly enough. Power, precision, durability, reliability...My only 9mm Bernina is the 820, and I don't do embroidery, so the only thing I can tell you about those 3 choices is that the 640 is being discontinued, so it should be available at a savings. The 450 requires a computer connection for embroidery, but the 640 and 730 can go off a USB stick. Good luck and I hope you enjoy your Bernina as much as I enjoy mine!