Differences between Agenda and NotePlan

If you prefer a quick summary, keep reading:

Agenda share some similarities in the sense that you can create notes which are referring to a specific date, and you can see your calendar events and reminders side-by-side with your notes in the right sidebar. You can write your daily journal or meeting notes this way. And this is where the similarities mostly end.

In addition, and different from Agenda, NotePlan focuses on task management and has Personal Knowledge Management capabilities. Everything can be combined in a single app: Notes (with PKM), Tasks, and Calendar.

The way NotePlan manages daily notes is also slightly different. In NotePlan, you get a blank daily note for every day in your calendar by default. You don't attach a date to a new or existing note. It's just there already. Further, your notes are saved in a completely different way.

Here is what else makes NotePlan different:

1. Tasks are first-class citizens

Tasks have multiple states (open, done, scheduled, and canceled) in NotePlan.
You can search and filter tasks under the "Review" option in the left sidebar across all notes.
You can schedule tasks from a project (undated note) into a daily note and see the reference at the top. Shortcuts and the user interface help you with this. This makes NotePlan a powerful planning tool. Connect project notes and your daily planning tightly.

2. Personal Knowledge Management

Link notes to each other using [[note name]] wiki-links. NotePlan will auto-complete the name of the note once you start typing. The backlinks to a specific note are displayed at the top of it. This enables systems like Zettelkasten (read here) and Second Brain.
NotePlan is built on Markdown and your notes are saved as plain-text files. We use Apple's CloudKit or iCloud Drive to sync your data across devices. So your notes are open, private, and future proof. Even your grand-grandchildren will be able to open your notes. If You can open your notes using any other Markdown editor.
Using the command bar (CMD+J), you can effortlessly search across all your notes and find anything you need.

3. Time blocking, Events, and Reminders

You can block time for tasks by writing something like "Buy milk at 3pm," and a block will be visible in the right sidebar. Read more here.
Create events and reminders synced to your iCloud calendars (Google and other calendars are also supported).

4. Customization

In NotePlan you can, not only change the theme from a variety of choices, but you can also customize themes and add Javascript plugins to the Command Bar.