I had an L1-B extension request inside the US and they came back with a request for more information. Honestly it looked like they were about to refuse my visa extension. I told the immigration lawyers that I'd be back in London over Christmas and they changed their tune. Applying through London, albeit with an L1 company blanket doc, took all of 30 minutes starting with review of the application and finishing with an interview where the person interviewing me obviously knew very little about my industry.

There appear to be wide discrepancies within the system that can be arbitraged.