At one point I used to have a set of DC 10-13X ANRs, a pair of Bose and a pair of DC X11s, so I've been able to compare all three reasonably extensively.
By far the worst of all were the X11s. Fortunately I bought them from a retailer who kindly offered me a full refund when he heard I was selling them second-hand shortly after buying them. Although they were reasonably sturdy and as comfortable as the Bose, the attenuation was terrible. Aviation Consumer recently did a test of ANR headsets and the X11s scored very poorly.
I now keep a pair of the DC 10-13Xs and a pair of the Bose permanently in the aircraft. As IO540 said, the attenuation on the DCs is a little better, but the clamping force is much higher than the Bose. The ANR on the Bose is very good at removing the low frequencies, but the passive attenuation on the DCs is better at removing the high frequencies as well. Because the high frequencies are important in making out human speech, I find I can understand ATC more easily and hence keep the radio volume lower when I'm using the DCs. For that reason they're generally my preferred set. Having said that, if I'm flying more than three hours or so, I'll use the Bose instead as they are far more comfortable for that length of time.
Incidentally, one other noticable difference is that if I'm playing music through the intercom, the sound through the Bose is much, much better than the DCs. Listening to music through the DCs reminds me of the old Dial-a-Disc days.
On the Lightspeed / Clarity Aloft question, Robert Goyer recently wrote up a
long-term comparison of the two in Flyer magazine. He tried out the custom ear moulds, but didn't find they worked very well. Of the two, he preferred the Clarity Aloft set.