In my opinion, PowerCLI and vCO are 2 products that serve 2 different purposes.
As we mentioned in our VMworld session, the Automation Triangle blog post by Andy Troup gives a good explanation.
To give an example:
- to perform a one-off migration from datastore A to datastore B, I would use a PowerCLI script
- if the same process has to be performed on a regular basis, I would encapsulate the PowerCLI script in a vCO flow.
So imho, it's not a PowerCLI or vCO choice, but sooner a PowerCLI and vCO collaboration.
Where you have to use the product that best fits your requirements.
See Seamless integration with PowerCLI and PowerShell plug-in for an explanation how both products can work together.