Welcome to Powermator,
I am not explaining any PowerShell here rather than explaining the main difference between PowerShell remoting and PsExec.
PowerShell, as powerful as it is, only works if the remote machine already has PowerShell installed and if PowerShell remoting is configured to allow remote access. But in exchange it gives you the whole power of PowerShell and the ability to execute comprehensive scripts remotely.
On the other hand, PsExec only requires network access to the machine and administrator privileges. No agents or preinstalled server applications are required. This is especially useful when dealing with older systems such as Windows Server 2003 and Windows Vista, which don’t have PowerShell installed by default.
Now you should know when to use psexec instead of PSremoring.