i've done both-depends on the quilt- really nothing to do with being a 'show quilt' or not- i've put them on before quilting for some of the kids quilts- they stay on better- longer.
it just depends- like everything else every quilt is different- and i back it, batt it and label it--individually.
i read some recommendations from one show that suggested that you actually write all of your information across the top(back) of the quilt so it is a permenent part of the quilt- then cover it with your hanging sleeve.
i've seen some show requirements where if you have a label on it they want you to stitch a cover over your label- containing different information- which you would remove after the show-
so every venue seems to be different too