I'm currently posting my long form newsletter both with Beehiiv and on Blogstack.io (Nostr client).
The main difference today for me is discoverability. My Nostr followers need to actively go to blogstack.io or habla.news to find the content.
I do post a short form note with a link to the article when I publish it and I'm hoping that blogstack.io or habla.news soon develop the capability to automatically post a short form note with the summary of the article so that my followers can, for example, see on Damus that there is a new article and can follow a link to it or maybe even read it within their client like @sitko was asking about