I don't think a long arm magically makes quilting stitches perfect. I don't own a long arm, but I know there are simple long arms that are only manually operated, with no stitch regulator, and than there are the nice long arms with the stitch regulator. I might be wrong, I would imagine that would make a huge difference.
I only quilt on my vintage domestic sewing machines. I try my best to make my stitches perfect, but I don't hold my own standards up to a computerized long arm. That is unrealistic to me.