gwmi VS get-ciminstance

I have a question on CIM vs WMI.  I read this on Microsoft's site:  

CIM: Common Information Model (CIM) is the DMTF standard [DSP0004] for describing the structure and behavior of managed resources such as storage, network, or software components.

WMI: Windows Management Instrumentation (WMI) is a CIM server that implements the CIM standard on Windows.

So is WMI is sub-component of CIM?  And if so do you still need Get-WMIObject?  

Get-WMIObject -namespace "root" -class "__Namespace" | Select Name 

gets the exact same information as this:

Get-CimInstance –Namespace root –ClassName __Namespace 

and when  you do a get-help get-ciminstance -examples Get-CimInstance seems to do the same type of work.  Just wondering if I need to stop using gwmi in favor if the new command.