I thought I'd save a few dollars and buy a pair of Zulu 2s over the Bose A20s - ostensibly because the Bose phones didn't have Bluetooth at the time - but after 12 months I came to my senses and bought a set of A20s anyway. I'll doubt I'll ever go back.
IMO, Bose A20as are better made, with better ANR, better alround sound and are simply more comfortable to wear for extended periods. They also seem to be more reliable with Bluetooth connections and have a better low-battery warning system. (Rechargeable battery life is about the same.)
After 12 months, the Lightspeeds needed new ear pads, the mic boom lost its ability to stay in place (it can't even be reversed for when you're sitting in the right-hand seat), and my ears always hurt after wearing them for extended periods - despite all that room, my ears always seemed to find the hard bits inside the cup to press against.
The Bose phones are a tighter fit - which helps with noise seal - but are deeper and seem to be a better shape (certainly for my ears). My wife likes the Lightspeeds because they don't have a lot of clamping pressure. I also can't fault their customer service. So now they're hers.