I like the Sennheiser 280s, but if you get 10-12 dB of isolation, you'd be lucky! Yes they isolate, but only to a certain extent. The ear protection muffs that fit over your ear and are commonly used for construction or industry are around 20-24 dB of isolation, but they are so tight on your head you'd go nuts after an hour of wearing them, the seal around the ears being critical to their performance. So noise canceling headphones like the ones you listed overcome the poor isolation of regular headphone muffs (because of added comfort) by counteracting the background noise with it's inverse within the muff, netting an additional 6-12 dB of isolation beyond the 10 or so dB isolation of just the muffs themselves.

So yes, you will hear an improvement in noise isolation with noise canceling headphones. Whether it's enough, that's for you to try out at a local stereo shop. I personally don't like noise cancellation headphones, they make my ears tired, but considering I make a living based on my ability to hear really well (I'm in pro audio), I'm more attuned to those problems.

In-ear earphones, especially when combined with custom molds for your ear canals give you the greatest isolation possible (as much as 36 dB or more, depending on fit) without having to resort to noise canceling circuitry. Because of their small size and good fit, they tend to be more comfortable for long flights.

Just for your reference, a 6 dB SPL gain or loss in level is technically double or half the volume respectively. Some in my industry argue that perhaps 10 dB SPL gain or loss is what the average person *perceives* to be a doubling or halving of volume respectively. dB SPL follows a 20log relationship.