I wasn't originally going to purchase the Airpods Max headphones from Apple. I had the Airpods Pro, which I liked because of the advent of spatial audio. They were portable and were great for going outside and having my music come with me. I didn't think the noise cancellation was a big selling point; it would have been more helpful, perhaps, if I worked and commuted within an urban environment. I could see using that feature on a bus or subway.
Unfortunately my Airpods Pro got a wash inside the pocket of my pants and while they worked for a short period before dying, the sound wasn't the same. It was unfortunate. I was angry about it and that was that. Money flushed down the toilet.
Some time before I'd purchased an AudioQuest Dragonfly Red mini USB DAC. I liked the sound quality. But using that with my phone was kind of a joke. It had to be threaded with two adapters: one to get USB out of the phone, and a second to translate its small mini-plug to a .25" plug on my Sennheiser headphones. Again, sounded great but far more utility when used with my iMac.
Then I was going on a cross country trip and lamented not having some noise cancelling headphones. In a last minute splurge, I came home with a Space Gray pair of the Airpods Max. I had watched the reviews. Yes, over time, your ears may sweat. They are heavy, at least compared to my Sennheiser HD650s. I like an open back design for the fact that there seems to be some air around your ears. But these had something the others didn't have: they were wireless.
The added benefit for me was that they could be used with a Windows PC for microphone and headphone; they connected seamlessly with all my Apple devices. The noise cancellation was pretty good. The most serious gripe has been the need to charge them or keep them "sleeping" in the cover that feels flimsy and laughably strange. At best, the cover prevents the outer shells from scratches. I sometimes take the Airpods Max to a work setting where I use them for phone calls and Zoom meetings. And inside my backpack the shell works ok.
Sound quality wise, however, I was interested in trying to decouple the sound from the wireless technology. How might they sound if they were tethered with a cord? I finally got the $35 cable from Apple that allows me to connect the 3.5mm jack to my Dragonfly, bypassing the internal DAC and using the conceivably better one in the AudioQuest device.
For testing, I listened to a set of tracks in a playlist I use for critical listening. I am familiar with these tracks and used Roon to drive them both through the Mac's "System Audio" wirelessly to the Airpods Max. Then I changed outputs in Roon to the Dragonfly and drove them via the Apple cable, the Dragonfly using one of the rear USB ports from the iMac.
Worth noting is that I listen to some high resolution music and the sample rate for the Airpods over Bluetooth has to be downsampled. With the Dragonfly, the music came over at full resolution. The Dragonfly does have a little more sparkle (and air) in the high end, but bass was equally reliable using both configurations.
I can't say why but some of these tracks have triggered some distortion. It sounds as if the music is being driven too hard, and the distortion was heard only when using the Dragonfly. I don't know if it's something to do with the AudioQuest's DAC or some mismatched levels. I was not using any of the digital filtering options in Roon. I played with the output level in Roon and that did not remedy the situation. It still sounded as if some tracks were being driven too hard. I tried listening both with noise reduction on and off and the "crackle" was the same in both scenarios.
Therefore, I have to admit, the sound quality with Bluetooth was superior in this comparison. Cut the cable. The convenience of being able to connect to computer, phone, iPad, etc., is pretty good. And in a work environment, having the ability to squash sounds around me was another plus when not using them for music.
N.B. The album I used to get distortion reliably was by Third Coast Percussion, Paddle to the Sea on Cedille Records and streamed via Qobuz.