Meh, this has been bandied about for years. Someone mentions their opinions somewhere (I think lately on a podcast) and a bunch of people **** about it, and nothing comes of it.
Bottom line, if it WERE possible, that there was a difference (which I don't, you have you hopsack rolling around in rapidly boiling wort, the AAs are going to be isomerized and mixed into the kettle as it tumbles around) it would be SO negligable as to be incalculable and not noticeable to our taste buds..
Not worth the time of day to stress about if you ask me.