Haahaha...OK. I went back and swapped cables back and forth a few times SE to BAL. You definitely have to turn the volume up a tiny bit when listening SE to match the BAL level. But sound quality-wise it's really close with a slight edge going to BAL. I can just hear a bit deeper in the mix and the vocal textures and sibilants are a bit more natural. The whole PRAT thing is a bit better with all the hues being a little better defined. BUT the SE is no slouch, it's really very close and I can't swear I would be able to tell the difference in a blind test. This is with my LCD-2's ONLY! So other phones might and probably will sound better or worse on a case by case basis.
I was listening to Dead Can Dance "Within the Realm of a Dying Sun" CD, track 4 "Xavier" so a very clean clear deep recording to judge with.