autodiscover record

Hi 

What should be the autodisover record in the internal DNS and external DNS(ISP) for Exchange 2013

Should it be a CNAME record or should it be a host record.

and which of these two powershell commands should i use 

Set-ClientAccessServer -identity EX2013 -AutoDiscoverServiceInternalUri https://autodiscover.mydomain.com/autodiscover/autodiscover.xml
or
Set-ClientAccessServer -Identity  EX2013 -AutoDiscoverServiceInternalURI https://mail.mydomain.com/autodiscover/autodiscover.xml