I have been given conflicting advice as to trying to stay out the box with composed looks, vs creation of more branded MasterPages. The former claimed as a recommendation so that customers can easily go from OnPrem to 365. I don't buy that given organisations want to create some form of branding identity on their SharePoint Sites, Intranet portals and so forth. Can anyone provide a reference to best practice guidelines around this? Surely having properly constructed MasterPages with corporate branding can port to 365 and don't result in loss of performance with page load times and usability etc?