i never worked with an Elna SU but i do have many vintage singer sewing machines (8 to be exact from the 1890s-1970s).
i never really sew or quilt on the vintage machines i just like to collect them even the FWs.
i only use modern sewing machines that have many bells. i wouldn't want a machine that didn't have needle up/down, a knee level, a needle threader, various machines stitches for machine applique, a large harp and throat, etc.
for me the hard part was finding all these features in a reasonable price and i purchased the Juki F600 for less then $800.