no comparison really
i just finished with bristol this past Jan. back when i started calling last year, oxford could not even begin to believe that someone didn't need the full monty course! i tried explaining it to them and they simply would not cooperate at all.
bristol's alex understands what the real world of aviation is all about and will actually listen to the customer!!!
at least in my book, that makes a world of difference.
but i must say that i needed some of oxford's books to help fill in some of the missing links in bristol's. but that may have changed with the continual revisions.
bristol's feedback was just as flexible as well. due to my experience i could take all the exams in any order i wished and they were more than willing to help.