When I went from my circa 1976 JC Penny machine to my Bernina my piecing accuracy did improve but what I really noticed was the experience of sewing increased exponentially. I compared it to going from a bare bone basics car to a luxery car. My Bernina would now be considered an "older model" because I bought it over 10 years ago. It is the 153QE so has some fancy computerized stitches but really I don't use them very much. Anyway I think my piecing improved a lot and things that were difficult for me before like Y seam and curves just seemed easier to do with the Bernina
Now if we are talking quilting getting a LA absolutely transformed my quilting. I was never very good at FMQ on my Bernina. I suppose more practice would have made me better but I just found it stressful and hard to devote the time for practice to something I didn't find thouroughly enjoyable. Not to mention the pure torture and drudgery I considered the sandwiching part.
The LA totally transformed that and when I don't have a quilt on the rack I feel something is missing from my life so it is easy to put in the practice time required to get better.