"Slightly better than normal in-ears, whilst stationary."2.5 starson by bworboys
Pros: Sound quality, nice base clarity.
Cons: - The difference between passive and active is hardly noticeable.
- Cord is too long and NC unit weighs against the ear buds, pulling them out
Summary: In-ear headphones already do a great job of blocking the outside noise, so that the cancellation effect isn't as noticeable as for the headphones with NC.
Plus you have to deal with the stupidly long cord, complete with NC unit which acts as a sinker, pulling your ear buds out if the NC unit is not clipped to your clothes in just the right way - this doesn't happen with NC headphones as the have the overhead band to support the weight. You can't just wake up, plug in and roll to work - you have to formulate a strategy of how to best accommodate the cord/NC unit or risk having to reinsert your ear buds every 10 paces. I'm sure it'll become second nature soon...
If you're thinking Noise Cancelling don't bother with the in-ear/ear bud variety, you can't even return them to the store!