6xx are better, don't look at rtings, here on reddit you will find all the experiences and real information you need.
Headphones
A community for discussion around all topics related to headphones and personal audio.
Rtings has a bit of a reputation of jumping to conclusions and iffy rating methods.
The SHP9500 and 6XX are a night and day difference to me. The 6XX has a very smooth treble representation, and I percieve it as sounding "more detailed" for lack of a better term.
The SHP9500 on the other hand has rather rough sounding treble, and even after experimenting with EQ, it always sounds grainy and harsh in comparison.
Now, the 6XX is a little more "narrow" sounding, but for me personally, I find much of the appeal of Soundstage loses luster after a while, and the other qualities of the 6XX shine much better
What does a smoother treble entail? Do instruments sound more detailed? Does this effect vocals in any way?
You may find an upgrade buying a headphone, you will not find an upgrade in digital audio codecs. Youtube already uses a transparent codec (Opus 192kbps), there's nothing above.
Don't trust rtings ratings, they are dodgy. Their measurements are ok but that's about it.
My first good set of earphones was the B&W Pi7 and at the time I thought they were great until I bought a Meze 109 Pro and a Sennheiser HD 600 and I thought those were great until I got the HE1000V2. My audio end game is actually all three of these headphones. Now that I go back to my Pi7s I now hear how bloated the bass really is compared to my great set of headphones.