When to extend and when to install.
USE A PLUGIN WHEN
The requirement is secondary to your main site The volume is modest You want one system to maintain Integration with your existing content matters
Examples: a small forum, a few courses, a simple booking system, a handful of products.
USE A SEPARATE APPLICATION WHEN
The requirement is substantial and central A plugin would need heavy configuration to approximate it The dedicated application is genuinely better at the job Volume or complexity exceeds what a plugin handles well
Examples: a large active forum, an institution's learning platform, a shop with complex commerce requirements.
THE TRADE-OFF
A plugin is less to maintain and less capable. A separate application is more capable and another thing to update, back up and secure.
THE PRACTICAL TEST
If the requirement is the reason the site exists, use the dedicated application. If it is a feature of a site that exists for another reason, use a plugin.
THE MISTAKE
Installing a full platform for a requirement a plugin would have covered, then maintaining it for years.
