For years, Bose has easily won our pick for the best noise cancelling headphones. However, right now it has serious competition from the AKG N60.
They offer more refinement than the Bose QuietComfort 25 and, for once, isolation that can stand up to the Bose standard. The N60 are very portable too. These are on-ear headphones, giving you great portability. If you want a full-size pair, though, you should definitely have a look at the Bose QC25.