@nickwhite:
I used to have a pair of Bose QC3s and I've had in-ear Etymotic ER6i. I've also tried the QC35's wired cousin, the QC25s.
The QC25/35 series is far and away the best ANC/PNC I've come across. Open cans led me to believe that ANC was more or less useless, not so with the QC[2,3]5 design.
I can't speak to your Sonys, but I used to have a pair of MDR700V-DJs. I remember the Sony's sound quality, and as I write this I wonder if it's even worthwhile since there's a massive tech gap between Sony's old cans and new generation, being overly bass heavy with poor high/mids. They were also super tight on my head due to, what was likely an innovation and useful at the time, collapsing spring design to fold the cups up.
I do a fair bit of travel for work and pleasure (80+ segments a year) that has exposed me to many aircraft including more-quiet cabins of the 787 Dreamliner from Boeing. Cabin noise was still a huge problem with my QC3s and I had all but given up on ANC being any good, until I sat next to a friend of mine one day and tried his QC25s. I knew I had to have them, and when I found out there was a BT version, my mind was made up. (Side note: I actually ended up upgrading for free as in a rush, I lost my cabin luggage in LAX that contained my QC3 cans).
Even the PNC is great, and to answer your question in a less storytime fashion, I find that both highs and lows are filtered out fantastically. This is particularly evident when you make a call with them. Not only can you hear the caller clearly despite relatively loud background noise (including having a fan/AC vent blowing across where the receiver mics are), the caller can, in my experience, not discern whether you're speaking natively via your phone's receiver or the QC35s (assuming bluetooth doesn't crap itself for some other reason).
I had a hearing test recently which indicated, as someone in their 30s who's been exposed to loud noises through recreation or working environments (data centres!), I've better-than-average hearing (i.e., minimal hearing loss). The reason I bring this up is that I've heard counter arguments that pan ANC, discreting listeners with the fact that they'd not be able to appreciate the full effect because they'd not be hearing high-frequencies due to induced, or age related, hearing loss.
My QC3s and Etymotics struggled with high-frequency, and the former with cabin noise, but the QC25/35 series do an amazing job. I fall asleep with just ANC on regularly, whereas before I'd to have activate an iOS white noise app, wear -35dB ear plugs, and turn the ANC on via my QC3s just to block out enough noise to get some rest.
The QC3s were largely OK when listening to audio, better than no ANC leading to bleeding ambient noise so intrusive it warranted cranking the gain, but the 25/35s are something else. Combine the ANC with using the optical aux wired audio, and you've great ANC
and awesome audio, without the need to subject yourself to unsafe volumes for long periods.
I tinkered with the BT stack via Bluetooth Explorer and configured my Mac to use AAC CBR vs. AAC VBR (the default), and I cannot tell the difference between the two. I tried with uncompressed FLACs and high gain, with V0 MP3s, AACs from iTunes, you name it. Very little variability that I could discern, which leads me to conclude:
1. BT is actually pretty good these days (pairing issues and dropouts notwithstanding, because even USD$399 Bose cans can't solve it, and from what I've read, the W1 chip in Apple's audo gear does a good job but is not perfect).
2. The QC series doesn't have enough definition in its drivers to bring out audio anomalies or deficiencies being broadcast from the source.
3. Even despite minimal hearing loss for me personally, age brings about a certain amount which may be covering issues.
4. I'm not enough of an Audiophile to give a **** (my membership to this forum only owing to my QC35 ownership and need to find answers to a number of issues I was having).
I'd be interested to hear what others who have owned your Sony's and now Bose cans for a period longer than is typical for a tech journalist reviewing the product have to say.
The only other cans I considered were the Sennheisers, but I've heard that the audio is muddy and bass heavy with the QC35s providing a better stage.
I can testify to the Bose obviously, but it's really noticeable when you're listening to a movie that has a AC3/DTS sound track. The ambient noises are discrete enough (via BT paired to my Apple TV 4) that I legitimately have taken off the cans a number of times because I thought the sound was originating next to me, rather than via the digital audio track.
The biggest objections that I've come across that you'll encounter when deciding to go down the QC35s to buy are:
1. BT sucks (it does, but when it's paired solidly it's fantastic).
2. QC35s have "x, y, z characteristic that makes them crap". This is a case of YMMV. What sounds good to someone else may sound terrible to others, and frankly, given that our hearing is a result of genetic disposition, unless there is an overwhelmingly negative view of the product's audio, you'll have to listen for yourself.
3. It's annoying because they have a non-removable battery. This is a non-issue. The battery lasts for ages, it charges very quickly via any USB power source, the battery indicator via the app and iOS are darn accurate, and worst case scenario, you forgo ANC and also plug the cans into aux. I had a pair of HD Sennheisers for quiet entertainment watching. They had removable batteries. Never did I bother to remove them.
4. They're bulky. Again, not an issue, Bose's folding mechanism means they are nice, compact, and most of all: flat. The carry case is robust and high quality.
5. The ANC doesn't do x, y, or z. Again, a case of YMMV. To me, whilst ANC will no doubt improve in the future, right now, the QC35s represent the best on the market.
A few comments of my own that you should consider:
1. Bose support in APJ (Australia in particular) is impossible and frankly, I think it's similar in other regions. I had to DM @bosescervice on Twitter, who then escalated my issues with the head of products in Sydney, to get someone to assist with the issues I was having. I emailed the ANZ team six times, and was left on hold for over an hour several times without ever actually having contact with anyone. I hope this is a case of the call centre being understaffed and not an overwhelming influx of customer issues.
2. BT pairing still sucks, and until Bose let you prioritize the auto connecting devices, as well as the number of paired devices to be <2, you will have issues due to devices taking the active source away from your existing source. Not to mention SDP profiles failing to switch resulting in callers being unable to hear you / you hear them or the cans being stuck on the Headset SDP so you can only enjoy the 8KHz mono audio until they switch or you power cycle them. Bose Connect may or may not make your life miserable, it depends on platform, use case, personal preference, and whether there is an act of god or other celestial body that should be unrelated to your audio experience but is the only logical explanation for the random issues (that Bose support can't reproduce) you're having.
3. Bose either don't post the release notes for new firmware images, or don't post full details. This leads to issues that may occur and you may not be sure whether they're from the software update or not (case in point, 1.2.9 was OK for some, buggered for others, and the point release 1.2.10, had similar results, with neither having publically accessible comprehensive release notes).
4. I had so many issues with pairing and switching sources that I believed my QC35s to be faulty. Upon replacement, same issues occur. Again, adjust your expectations because despite Bose's best efforts, BT is still unpredictable. I hope Apple opens up their W1 chip to everyone as it sounds like it's almost solved these issues.
5. If you're in the Apple ecosystem, turning off handoff between your devices and Mac
appears to be more reliable. I get less/no dropouts, less audible artefacts, and more reliable source/profile/device switching.
6. For the same reasons as above, turning off
voice prompts appears to be more reliable. It's tedious trying one thing and then testing over and over again. By the 30th test case I devised I was certain that I was no better off than before I started, so again, YMMV.