I don't know anything about the 7700, but I have had my 6600 for 6-1/2 years, and I wouldn't give it up for anything. I have it professionally cleaned every 1-1/2 to 2 years and have made zillions of quilts and other things with it. It truly is a work horse! My repairman told me it is the most popular of all the machines he services! Before I got my longarm, I used it to FMQ all my quilts (including king-sized).