Comparing the noirs and the k371s, do you find the noirs better or they both just excel in different ways?\
Definitely excel in different ways.
Some people find the 99 Noir sound signature to be very dark. To be sure, it is an exceptionally warm sound signature. I would say, however, that it makes them more chill than dark. The bass is very present, but isn't muddy. You feel it, but its tight. It doesn't take away from the mids. I can't really say much to the highs though. I think they do their job well, you get a lot of those little details, but they're not necessarily up front. 99 Noirs are, in my opinion, more comfortable and I like the overall build quality and aesthetic of them over the K371s. The biggest advantage of the 99 Noirs over the K371s is that really smooth over any track and make it sound good. Again, they're a chill, "lay back and relax" type of headphone. Though, they also do have better depth and imaging than the K371s. A couple times a vocalist would join in with a weird, quiet whisper sort of singing and it scared the crap out of me because I legit thought they were standing behind and to the right of me. You just don't get that with the K371s.
The K371s are still warm, but they have a more aggressive presentation of detail than the 99 Noirs. The 99 Noirs have detail, but they aren't really in your face about it. That's not to say that the K371s are, not like something like the DT1770s, but more so than the 99 Noirs.
Even though they're both closed-back dynamic driver headphones, its really hard to compare the two accurately because they have such different sound signatures. Even though the K371s do have a warmer signature, I still consider them my analytical headphone because of the presentation of detail. I'm more likely to wear the K371s if I want to intently listen to a song and pick out those little details, etc. But, if I want to really
feel the music and just enjoy it, I go 99 Noirs. Maybe they're too warm for a lot of people, but its just an enjoyable, musical experience for me across a lot of genres.
That's to be expected though. The AKG K371s are advertised as a studio professional headphone, the 99 Noirs are not.