The biggest advantage imho of PowerShell Core is that it runs on more platforms than PowerShell 5.1.
This includes several Linux distriutions and MacOS.
Due to that fact, you can also run it in a non-Windows container.
There are, for the time being, a number of limitations, in the sense that not all PowerCLI cmdlets and PowerCLI modules, are yet ported to PowerShell Core.
This is partially due to the fact that .Net Core doesn't provide all the API that are available in the Windows .Net libraries.
One of the most noteworthy are the CredentialStore cmdlets.
These are missing, for now, due to the fact that .Net Core doesn't not have the DPAPI methods.
On the PowerCLI Core documentation page, you can read up on the above in more detail.
Blog: lucd.info Twitter: @LucD22 Co-author PowerCLI Reference