I owned both and ended up selling LCD-2.2, even though they seem to be more technically capable, HD650 while having pretty close signature overall, wins hands down in comfort department. I also liked soundstage and instruments positioning out of HD650 better.
Old with new HD650 story is the difference between worn out and new pads, Senns also started stuffing them with firmer foam which adds more treble sparkle.
Check out this thread http://www.head-fi.org/t/197776/sennheiser-hd650-appreciation-thread/11520#post_9299137, I've experienced that "treble/soundstage transformation" after installing new pads first hand. In fact after that they got sooo darn good I am barely touching any other phones.
Interesting, that graph there definitely tells a different story with the improved treble after the new pads installed. This may also somewhat explain why the 2 pairs of different pads I have for my HD600's. One pair is very soft, quite comfortable and as soon as I put it on the pads hug onto my head. The current pair of pads I'am using are bit more firm and harder. It's the difference of foam vs feathers. I prefer the firm one.