I agree, it usually is not the machine. However, I have had several different brands, Singer, Viking, and now two BERNINIA's....first a 180 (very good model) I have recently upgraded to a 440 with embrodiery.....By far, the very best, features, attachments, ease of operation and yes, accuracy.
Remember, measure accurately, use a guide (there are several) and practice. (mark fabric, mark your machine, start slow and gradually increase speed, and have fun, Rome was not built in a day).
Hope this helps, I am truly a Berninia Girl now!!!!!!