Over the years, the Drupal and Plone platforms have been converging toward the same feature set with a TTW content type creation system and a component-based architecture.
While Plone has always had collections, Drupal has recently added views into the core. Both collections and views offer a way to provide canned queries or smart searches for content that you can now use in blocks or tiles around your site. The Plone Mosaic implementation will make Drupal administrators more at home.
However, to this date (Fall 2016), Plone still leads in terms of workflows, roles and permissions. Plone also has an edge through the new Diazo system that allows through the web theming whereas Drupal continues to offer a more traditional theming mechanism.
Drupal 8 security is very vigilant about security with a team of 40 people on the security team, and as a result, the Drupal security record has been improving.
Drupal is more approachable by new developers thanks to specialized hosting providers (e.g. Pantheon) that cater to Drupal. They guide developers through best practices for development and production deployment. On the other hand, the Plone hosting story is still very much DIY.
Drupal also has more add-ons and modules, but this is a double-edged sword, as the more modules you install, the harder the future migrations will be. Plone's core offers way more features out of the box, which means they are maintained by the core development team. Migrations between versions will be smoother.
At the end of the day, if you have to choose between the two, it comes down to your priorities and your needs: if you have specific requirements for workflows, Plone is a better choice. If you don't have very technical staff, Drupal may be a better option.
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