In the early 90's I worked for a Bernina dealer who also did custom dressmaking and alterations to survive. I purchased three different machines from her. We used bernina machines in the shop to do the sewing for customers. I learned early on that the machines that did the biggest decorative stitches and then the ones that also did embroidery had the least stable straight stitch. When the 1630 came out that did the really wide decorative stitches I did not like working on it because it could sew in 16 different directions. To my "quilt" oriented mind that meant "wobble". I was able to purchase a 1260 with my employee discount. While it did lots of decorative stitches it was much more stable in the straight stitches I needed for quilting. I also own a Bernina embroidery machine but it is an entirely seperate machine that only does embroidery.
If you are only interested in piecing accurately look for a machine that does basically straight stitching.
I don't machine quilt anything bigger than crib or lap size as I am basically a handquilter.