I liked them both, but sound is a very subjective topic. I can give you a rough summary as it wasn't that long ago - I only used DAPs as sources with these headphones (M17 and DX240 w/AMP8):
Lows - I liked Radiance more, because midbass was elevated a bit, liked it had more weight behind it, however I think it did overshadow subbass which didn't happen on D9200; also as far as I remember, bass on D9200 was very high quality, textured and nicely layered all the way down
Mids - both of these headphones sounded reasonably natural to me, but I thought D9200 is a bit mid forward headphone (or maybe I'm just sensitive to these frequencies, I don't know) and could get sibilant with voices on couple of songs; despite that I liked it very much, more than Radiance - some songs were a hard listen on D9200, but others were truly magical; Radiance was very neutral sounding and to me and never got sibilant or shouty
Highs - treble on D9200 sounded more extended and it was very airy presentation - I think most people would prefer it over Radiance, although I personally didn't feel like I was missing too much with Radiance
Soundstage - D9200 was very wide (wider than many open-back headphones), but not very deep or tall; Radiance was not as wide, but sounded taller to me, also not very deep
Imaging - this was a strong point with D9200 and to my ears was clearly better; because of that I really liked listening to Hotel California on D9200
In the end I sold both of them - I have a big head and D9200 was not very comfortable, I could only listen to 30-40 min before my head started to hurt (headband is very hard and has some sort of a sharp edge right in the center) - I tried to fix it with extra padding as I liked this headphone, but because of my large head earcups no longer covered my ears anymore so I had to sell it. After that I've gotten Liric and Stellia, so I decided to get rid of one more closed-back. I AB'd T5.3 and Radiance a lot and came to conclusion that T5.3 is a better headphone - it has the same physical, hard-hitting midbass, is just as detailed, but on top of that it has bigger soundstage (both wide and tall) and is way more comfortable.