Think of Bose's QuietControl 30 ($300, £230 or AU$449) as the ultimate neckband-style Bluetooth headphone. (That's the style that looks like a horseshoe draped around the back of a person's neck, which LG pioneered with its top-selling .)
This is why that's important: If you buy the QC30 thinking it's going to sound exactly like the QC20 and offer the same level of noise-canceling, you may be disappointed.
The wired QC20 sounds a little better, with slightly fuller bass and more dynamic sound. The QC20's noise-canceling is also a little stronger, as is that of the full-size wirelessmodel.
The QC30's noise-canceling is designed to be adjustable, which is why the product is called QuietControl. You can raise or lower it by pressing a set of button on the inline remote or via the Bose Connect app for iOS and Android devices. Most people will keep it at its highest level, but if you're running and want to hear traffic, you could turn it completely off.
In terms of competition, JBL has a headphone called the Everest Elite 100 ($200) that's a wireless neckband-style headphone with active noise-cancellation. This Bose sounds better and has much better noise-canceling than than the JBL -- it's really no contest.
So even though the QC30's noise-canceling isn't quite as effective as the QC20's, it's comparatively decent and when I wore the headphone in the streets of New York, it muffled a lot of ambient noise. In the office, the headphone cut out fan noise, but I could hear people talking around me, albeit toned down. The QC20 was slightly better at muffling everything, but I could also hear people's voices around me (I wasn't playing music during the test).
If you're thinking of using the QC30 on a plane, be warned that it doesn't plug into an in-flight entertainment systems because it doesn't have a wired option (like every other neckband-style Bluetooth headphone I've reviewed). So if you're a frequent traveler, the QC20 is probably going to be the better bet. However, the QC30 is an excellent everyday wireless headphone, as well as an excellent wireless sports headphone.
Not only does the build quality seem quite sturdy but the headphone fits very comfortably, with a semi-open design. By semi-open I mean that you don't jam the earbud into your ear. Thanks to Bose's Stay-Hear+ eartips, which come in three sizes, the bud sits more loosely in your ear yet remains securely in place. (I call it "semi-open" because the fit is fairly snug, but the tip doesn't completely seal your ear canal like a noise-isolating in-ear headphone would).