Ranked in these QuestionsQuestion Ranking
Pro Sync with other Apple devices via iCloud, other cloud/email services
It syncs with iCloud, and surprisingly, also with Gmail and possibly other services too.
It's a default system app, making it easy to find and use since it is already installed.
Pro Rich-text editing
Allows for simple text formatting and making TODO lists with checkboxes.
You can add files to notes and then filter notes by attachment types.
Pro It's fast, and syncing is very dependable
The app launches quickly on both Mac and iOS, it also syncs quickly (in seconds) and very dependably across different Apple devices.
Pro Supports sharing
Pro It remains simple to use with a gentle learning curve
Despite the significant new updates in iOS 9 and iOS 10, you can start using Notes immediately, then try/master new features with ease — definitely a gentle learning curve.
Con Cannot export to a format that can be imported again
This makes it obscure and cumbersome to back up your notes as files that could be managed by your backup system. You can export to PDF, but not in bulk; and this isn't the native format that you can easily recover with.
Apple compounds the problem by using some undocumented format for notes. You can, however, back them all up by backing up the files found in ~/Library/Containers/com.apple.Notes/Data/Library/Notes