While the HD 238 headphones don't isolate noise as well as over-the-ear models, they do well to muffle outside noises -- this is called passive noise cancellation, in contrast to the active noise cancellation of some headphones that requires an internal battery to work.
In reviewing the Bose OE2, I noted that they sound more natural and don't suffer from "Bose bloat," a term coined for its obtrusive bass boost. These Sennheisers exhibit similarly detailed sound and ample but not "bloated" bass. These are a touch on the warm side and will appeal to listeners who prefer more-laid-back, less-aggressive headphones with edgier treble.
Keep in mind that you shouldn't expect the same kind of sound from these Sennheisers as you would with higher-end models that cost well over $200. The point here is that the while the 238s don't offer great sound, they do deliver very solid performance for their price.
The Sennheiser HD 238 headphones actually carry a list price of $139.95, $10 less than the Bose headphones' list price. Bose headphones are very infrequently discounted, however, and a quick CNET Shopping search finds these Sennheisers for less than $75.
The problem is, that deal is unlikely to last. These headphones have been discontinued, presumably replaced by the Sennheiser HD 239s (list price $120). (Sennheiser also makes the