I think one experiment you haven't done and hasn't been mentioned could be potentially useful: try to locate 5 or so of your favorite pieces of music, regardless of format. then try to find them on the other format. do your listening in a less analytical way, simply playing the music as you normally would. if there's a meaningful difference (to your ears) it really should jump right out at you. the point of the experiment is that since you are theoretically very familiar with the music, you are more likely to hear the differences between formats (if there are any).
it seems to me that all of the talk about the quality of the pressings and masterings etc., while relevant, ultimately are a distraction from what you're trying to determine; those issues are present with both digital and LPs and you're trying to figure out something which transcends that question.
it seems to me that all of the talk about the quality of the pressings and masterings etc., while relevant, ultimately are a distraction from what you're trying to determine; those issues are present with both digital and LPs and you're trying to figure out something which transcends that question.