Using unique or duplicated blogs for guest blogs?

Hi all!

Lately I have contacted quite a lot of websites that are potentially interesting for backlinks (good and relevant content). I asked them, if they would like to receive a guest blog. I was surprised by the amount of positive reactions. So I am busy with writing at the moment and I was wondering what the best method would be to get the job done. Would that be writing only unique blogs or sending multiple of the same blogs out there? Most news articles are placed also as duplicated content on different sites for example.

Looking forward to your insights!