For Travel?
I fly 50k to 85k per year, and have had Bose and Sony NC headsets. The fact that the bose don't fold up to stow bothers me about them. I went back to my old fold-able sony's unless I am going on a flight over 4 hours.
The bose are the best, but aren't worth the price. Check out the Sony's for 90% of the NC ability of the bose for less cash. Look at Panasonic for even less money and still a good option.
They don't block out everything, just the low frequency repetitive noise. I can actually hear the people in the next row talking better with the NC on than off. If you want real silence you should look at the in-the ear noise blocking headphones like the etymonics.