One thing I do know, all machines differ a little bit. For example, a 1/4" seam is not going to be exactly the same on your Janome 2010 and your Jamone 720. So, if you are starting an important project, and keeping your seams consistent is important, you need to start and finish on the same machine. Otherwise there may be maddening subtle differences when you try to match seams up or in the width of your borders after sewn.