Why should I create a communication site, while I can also publish the pages in the Teams site?

tom_s1865 

A team site is meant to collaborate in, so all members of the site create content and have more or less the same permissions, but access to this site is typically limited to few people. You can even easily share content externally. To make collaboration easier, you automatically get an M365 Group, a shared Mailbox and all the stuff @Barbarur mentioned.

A communication site is meant to be open to a large part of, if not your whole organization. A few content authors create content, but a but a larger number of people consume that content. If you provision a communication site, then you just get the site, nothing else. (So no M365 Group.)

In terms of things like available webparts, team sites have more webparts. As a team site has a group, so you get some webparts that make only sense on a site with a connected M365 Group like a "Planner Webpart".

The following webparts are only available on a team site

• Asana
• Bitbucket (and Bitbucket Server)
• GitHub (and GitHub Enterprise)
• Google Analytics
• Incoming Webhook
• JIRA
• Office 365 Connectors
• Planner
• RSS
• Salesforce
• Stack Overflow
• Trello
• UserVoice

On the other hand, if you want to use some other features that are usefull if you build an intranet, then you need your site to be a communication site.

An example is the "Home Site". This needs to be a communication site.

If you narrow your view down to a single site then a team site has more features that a communication site and you would not really need a communication site template.

But team sites are preconfigured for collaboration and come with M365 groups and some other settings build in. These make team sites difficult to use if you i.e. want to create an intranet that contains hundreds of sites.
Then you would have hundreds of M365 Groups that you either don't use at all or that you would need to keep synchronized with the same users.

With communication sites you would just add the same "Active Directory Group" to the "Visitors SharePoint Group" of every site to achieve the same effect.

So if you view at all of your sites  in a tenant at one, communication sites take less ressources and are easier to handle in the cases where you don't need all the collaboration features.

Best Regards,

Sven