It depends on the number of sites they each link to with at least one followed link. The more unique websites a site links to, the less so-called “DR equity” it can pass.
So, let’s check the Linked Domains report for each site and filter for ‘followed’ links only.
3 guardian linked domains
4 imdb linked domains
It looks like The Guardian links to around 50x more sites than IMDB (272,218 vs. 5,256). Therefore, the link from IMDB would increase your Domain Rating more than the one from The Guardian.