One feature I enjoy on GitHub is the compare page.

https://github.com/fedora-infra/noggin/compare

This lets you compare branches, tags, and commits.

Pagure seems to have a similar page for setting up a pull request, but it appears to be limited to branches, and requires putting the branches into the URL from the start, as opposed to having a generic page to set up the comparison you're looking for like GitHub has.

Please consider adding this to pagure.