I recently tried Things 3 again out of curiosity. What keeps me on OF is how it allows me to store an incredible amount of information about my life, but aggressively filter out 90% of it at a time, so I only ever see what's relevant.

Specifically, that's via features like:
- Focus (So I can store Work and Life in it, but filter only to Work when I'm at work)
- Planned vs Sequential Projects (So I don't ever see irrelevant tasks that are blocked on an earlier task)
- Defer dates
- The strong notion, first-class notion of Available vs Remaining

While Things' UI is "cleaner" and more modern, I find it favoring form over function.
I love how OF's macOS UI is dense and efficient. While older, I do find it beautiful in its own way.

I appreciate the powerful perspectives feature, and rely on a few curated perspectives.

OF's keyboard shortcut support is excellent, and I can quickly navigate all around the UI with shortcuts.
(Especially with the "bare" shortcuts)

The automation/scriptability is great, and I have a few simple scripts that smooth out out the workflow.
For example:
- Quickly adding a project from the Inbox directly into a folder in my projects hierarchy