Your content should live in HTML widgets when:

• Content only lives in one area.
• Versioning is not important.
• Content is highly unlikely to change. 
• Content does not need to be managed (e.g. "About this Area").
• Content does not require interaction (likes/comments/etc.).
• You're not obligated to archive content due to compliance (e.g. corporate or regulatory body requirements).

Your content should live in wiki articles when: 

• Content needs to be surfaced in more than one area.
• You care about the version history.
• Content has an owner (requires edit access to manage the content, ability to respond to questions/comments, etc.).
• The content can be bucketed into a wiki channel with other content (e.g. Attendance Policy within HR Policies).
• You want to track read receipts.
• You want to allow likes/comments/ratings/tasks.
• You're required to archive content due to compliance (e.g. corporate or regulatory body requirements).
• Your organization has determined and set archiving policies in the digital workplace.