I'm on a Beyer kick right now. It started when I got my old 250-ohm DT-770 Pro and DT-990 Pro out, which I've had for more than 12 years now. I opened them up and made sure the foam and drivers are free from debris, refurbished them with new pads and did some work to stabilize and repair a cable issue on the DT-990 Pro. I ended up giving the DT-990 Pro to my oldest kiddo, who is loving them, and decided I'd check out the 600 ohm 880 and 990 since I'd never owned those two myself.
Comfort is extraordinary with the Edition cans. When adjusted for my head (and it's a big head, friends, I pull each earpiece out until seven of the dots on the adjustment piece are visible), they pretty much "disappear" when the music is on. Faaaar less clamp than my other, beloved Sennheisers, more comfortable IMO than Audio Technica's wing system on the ATH-A990Z that I've got with pads that breath a lot better so not turning my ears sweaty over time. It's hard to compare them to the Q701 and K712 that I use, because they have such different designs. I'm a fan of the AKGs' fit and find them comfortable for long wearing as the large circumaural pads spread out the clamping force very well. The Beyer Edition headbands are much more robustly constructed while being comparably comfortable but with less of a clamp, albeit different in how they sit on your head.
I love their looks, personally, they really do have a premium appearance over the Pro models. I like the shinier appearance and metal grilles on them very much. I know some people disagree, but I don't mind the metal fins above the adjustment piece on the headband, plus they serve a functional purpose of distributing the clamp even better that I do appreciate.
About the sound:
I think there really is something to the 600 ohm drivers being a bit better in their technical performance than the lower impedance ones. Well, I don't want to make too much of it, as the sound signature is overall way more similar than different, probably as expected, and the 250ohm hardly suck to begin with - but the 600ohm drivers do seem to reproduce the signal with more fidelity. Bass is better controlled and treble seems more precise, while the midrange is so clearly presented even with busy material (though the 880 brings it forward quite a bit more than the 990, without EQ). Listening to complex, layered mixes with lots of carefully positioned treble elements playing against a fluently moving bass backdrop with prominent midrange melody elements there's no congestion and you can easily hear small details like where specific punch-ins and punch-outs occur for recorded harmonies and enhancing instrumental elements that are mixed low, clearly and with precision.
A note on EQ - I like it, I use a Schiit Loki Mini+ and EQ by ear (but with the frequency response of the cans in front of me as a rough guide). My philosophy there: I've worked with audio for almost two decades professionally, used several different monitoring rigs in different environments in that time, and I've formed the personal belief that absolute accuracy is less important for translatable work than utter familiarity with a huge variety of material on your preferred reproduction system. All speakers and rooms (and all headphones and head+ear geometries) differ, there will always be some things that are hyped or reduced to different degrees; and if that's not enough, we not only hear differently due to our unique ears but also we differ in just how our brains relate to the incoming signal & what we like! Ultimately, it comes down to understanding how things sound on your gear and experience as to how that will translate to different listening environments with different reproduction equipment. I think that bears more fruit in the long run than chasing holy flatness. Enough detail to be truly revealing is crucial for audio work, and you don't want outright deficiencies anywhere, but great records have been made that translate across many different playback systems with allll kinds of monitoring setups.
Anyway, sorry for that aside - if I didn't have EQ I'd like the DT-880/600 better for sure, as they are more to my tastes in their default sound signature which is more balanced and linear in important frequency ranges while still retaining extraordinary treble clarity (hey, Beyer is well known for that treble, and I personally think it's great - "analytical," as they say). The DT-880/600 without any additional tone shaping are already an impressive listen, and are fast becoming a favorite for me that I anticipate using as a quick reference for certain things when recording. BUT, the DT-990 with a high shelf somewhat reducing the peaky treble a bit and boosting the midrange to bring it forward from the default recessed presentation results in an overall sound that is so full & powerful, with great soundstage and accurate positional imaging within it. There is definitely more body to the lows than the DT-880/600 manages, even when EQ'd. Bass is great from the DT-990/600, and the treble is still extremely revealing when tamed slightly (by default, it can be peakier than is comfortable to me if the material has some sibilant qualities already).
Each one of them has their own tuning as far as the enclosure and dampening goes, and EQ is not going to change the inherent resonant frequencies or other characteristics that are engineered into them, so having both on hand and playing to their strengths is a winner for me - and thankfully a lot less expensive in 2023 than the same pair would have been back in the early 2000s when I first got into audio.
Something that really impresses me is these are fairly venerable drivers by modern standards, and yet they still have strong technical merits and great sound quality that does not seem out of place among today's offerings at all.