I've tried the Bose QC and the Shure, and IMO the latter is better at removing ambient sounds. The Shure does not use active noise cancellation like the Bose,

I've tried the Bose QC and the Shure, and IMO the latter is better at removing ambient sounds. The Shure does not use active noise cancellation like the Bose, but I think it is more effective simply because it fits snugly in your ear like a set of ear plugs. (It's also more uncomfortable because of that.)