Great question @Johnnydn.
If you published your original article on another Medium publication, AFAIK you’d have to remove it from that publication for it to be featured on HN, as Medium won’t let the same story live on two publications.
If, however, you’re referring to a publication/blog outside of Medium… it’d need to be a story we think has the potential to shoot the lights out in terms of adding value to our audience, as we’re naturally going to favour previously unpublished content.
In terms of potential exposure, when you say ‘new vs. old’ - are you referring to new vs. old content, or the old platform vs. Hacker Noon 2.0?
Either way, HN currently averages around 200,000+ daily visitors, and 8,000,000+ monthly pageviews. And, if your article’s not getting the exposure you feel it deserves post-publication, you can always chat to the editors about what we can do to amplify its reach.