Someone here posted that there is a difference, I forget who. According to their post, junior (and/or local officers in a foreign land), can take care of and approve simple applications while complex applications flagged by some criteria are queued up for a senior officer (really Canadian) to review and approve. The OP of that thread was ticked that their file was considered "complex". How they would find out, I don't know.
This is all hearsay on my part, but it certainly explains some discrepancies in varying timeliness from the same VO.