What I mean by "critically revealing" is, which of the headphones that you own are the most revealing in terms of allowing you to hear differences in upstream gear? For example, with which of your headphones can you hear differences between DACs most clearly? Amps?
While you may not be equipped to do true A/B tests of amps or DACs on a given set of headphones, please try to do some listening to the "A" and "B" (two different DACs for example) through the 'phones in fairly quick succession, in order to bring a measure of objectivity into the discussion.
In my experience, my Sennheiser HD800's seem to show DAC and amp differences more clearly than my other headphones. I am wondering if the well-known high frequency emphasis of these phones allows these subtle differences to be highlighted. Also, my LCD-2's sometimes reveal subtle differences in bass quality that I can't hear with other phones; I assume this is because of the flat response, low distortion and transient accuracy at low frequencies of these headphones.
[In fairness, I have recently bought some Stax electrostatic phones, but I have not done any A/B stuff with them yet, I have been too busy just listening to them. So, maybe the Stax's are the most "critically revealing" of my collection, but I haven't checked that out yet.]