With current D8 status, what's the decision tree for creating a new content entity type versus creating a Content Type for the "Node" content entity? We have seen four years and Drupal 8's first release since the accepted answer was written for the question "When is it appropriate to create an Entity versus just adding a new content type?"  And, entities are more central to Drupal 8 than they were in Drupal 7.(RefB, RefC, RefD)

In this new Drupal 8 world, what is the decision tree for creating a new content entity type versus a new Content Type for the content entity of type "Node"?  

As you consider a response, please consider the following:


Is a new Content Type for the content entity type of "Node" still appropriate in 99% situations versus a new content entity type?  
Does the decision tree now include more, better, or clearer reasons to veer away from using the "Node" content entity type and instead create a new content entity type?  And if yes, what are they?  Do they include:


Performance?  
Security/permissions?  
The number of modules that work with Node-entity-type Content-Types and do not work with other content entity types?  

Perhaps -- based on the previous accepted answer that is referenced above -- the only general reason to do a custom content entity type is if you want to group Node data, e.g. with taxonomy terms, or otherwise annotate Node, e.g. with comments?


Module compatibility seems like a particularly interesting consideration for a decision tree.  At present, few of the most-installed modules have a release for 8.x that is not merely alpha, beta, or rc (a release candidate).  And it seems difficult to identify how many of them will work out-of-the-box with a new custom entity type versus a new Node-entity content type.  There does not appear to be a project attribute to distinguish between those that are "written for entities" versus "written for node entity content types".

Take a look at pathauto, which is currently the fourth-most installed module of those that have any kind of 8.x release.  Folks are working hard on a 8.x version that generally supports entities and not just Node-entity-type Content Types.  But what about all the other modules?  And will modules that support entities going to generally require custom content entity types to have module-specific "hooks" before the module will work with them?  (Versus how the modules may just work straight out of the box with new Content Types?)  That appears to be the kind of challenge the pathauto team is working with, and perhaps it is a reason to veer away from a custom content entity type?

It might also be worth mentioning that Drupal 8 core contains a UI for creating new Content Types for the content entity of type "Node", but it does not currently contain a UI for creating new content entity types. (RefX, RefY, RefZ)
Decision tree for choosing between creating a new Node-entity-type Content Type versus a new content entity type:


Are you a programmer, or do you have easy access to a programmer?  


If no, then you are presently pretty-much limited to creating new Node-entity Content Types.  (There isn't a UI in core for creating new content entity types, and the Entity Construction Kit (ECK) contrib module currently only has an alpha release.)
If yes, then continue...

Do you know exactly which contrib modules you want to leverage for your data?  


If no, then the safe bet is probably to just create a Node-entity Content Type.
If yes, do those modules already support the custom entity type(s) you're considering, or are you willing to help enhance them so they will or recreate the desired functionality in your module?  


If no, then just creating a Node-entity-type Content Type may be best for you.  
If yes, then continue...


Will the actual content data that is enabled by your module merely help group or annotate other content data?  (So that it will seldom be viewed on its own.)


If yes, then consider whether your module is like the existing entity types for taxonomy terms and comments.  If it is, then a new entity type may be a safe bet.
If no, then continue...

Can you clearly articulate why a new Node-entity-type Content Type will not work for you?


If no, then your safe bet is to probably just create a new Node-entity-type Content Type.
If yes, then continue...

Lastly, are you sure that you can't just extend the Node-entity-type and that you want to recreate all of its useful functionality like CRUD operations?


If yes, then go ahead and create a new custom entity type.
If no, or if you're not sure, then you probably want to engage some experts to help you decide.



Notes:


This decision tree does not consider performance or security.  I'm not sure if or when a new custom content entity type would perform better and be more or less secure than a Node-entity-type.
Even if this tree is a good answer, it will probably not remain one over time due to updates in Drupal core and contrib module releases.  StackExchange doesn't seem to accommodate how the "best" answer today may not be the best answer tomorrow.)