My first machine was a Gammill Optimum Plus, it was too heavy a machine for me (I am 5'2"). I had problems with tension and getting good customer service (others may have a different experience). I had problems with stitches flat lining and never could get it straightened out. Would I buy another Gammill?...no Do I like the Statler System?...yes Would I base my purchase because of the Statler system?...no because others are just as good.
I have had a Millie and traded it for a Freedom Sr (I think it moves more easily) and my second machine was a Liberty (when I was in business). I really like APQS machines, I love the customer service and all the help provided. I considered buying an A-1 because they really move the best on rails, but I wanted more throat space, my friend has more problems with different threads types on her A-1 and I didn't like the stitch quality compared to an APQS.
I have a CQ because at the time it was really the only option with an APQS machine. If I were to buy a different computerized system I would definitely consider an IQ. You can have a statler system put in an APQS machine, but they have to strip out the insides and then it is no longer an APQS machine.
IF YOU are really serious about purchasing a machine...YOU NEED to attend a MQX or MQS....YOU NEED to try every machine available and these shows are the place to do this. This is a lot of money you will be spending, do it with knowledge on your side. I know you can go to the APQS booth and play for hours, testing the machines. They are very helpful and don't be afraid to come back and come back to ask and play.
Every one is different, every machine feels different, everyone fits one machine better than another and every one has their own opinion as to the best machine. For me, APQS has been the BEST.
Take all the opinions, go to a show and learn. Then make a decision on which machine to purchase.