Today you can find three Common Data Service (CDS) connectors in the Microsoft Flow platform (https://flow.microsoft.com).

Microsoft is making an amazing progress on this platform to add new features and improvements. This is probably the reason today we have those few options.
Number 3 is very easy to recognise because the name will include”experimental” in its label once you hover it:

However, the other two connectors names are the same: “Common Data Service”. One of them is the main current stable one and the other is a legacy one. The best way to understand which one is what is looking at their triggers and actions and compare them with the documentation:

If we look at number 1 (currently main stable), these are the operations available:
However, if we look at number 2 (legacy), the operations are different:
And what about the Dynamics 365 connector?

It is now officially confirmed in this article, the Dynamics 365 has been deprecated and it shouldn’t be used any more. Instead we should use the Common Data Service connector described above (number 1). This is another good sign of how the Power Platform is surrounding the Dynamics applications.
Hope this helps you to choose the right CDS connector 🙂