Not that my subjective review matters, but vs the Aria, the RED is more 'natural' to my ears. Bass is clearly further extended on some notable tracks giving 'atmosphere' to some notes rather than heavier bass exactly.
Much more capable of high SPL.
When EQed to Harman 2019 target the Aria sounds 'enhanced' a little. Its perhaps a little more exciting initially, but not sustainably to my ears (due to my job I have thousands of hours on them)
The RED doesn't sound as good EQed to Harman 2019, but I find is much better to the latest crinicle target with a +3 db from 250hz down shelf.
this target isn't as effective on the Aria.
THe RED is the best IEM I have heard to date.
Both are Leagues ahead of my AKG 371 over ears.
THe REDs are the smoothest non fatiguing IEM I have heard (particularly with female voice), but I suspect it is possible to get the tiniest bit smoother in the mid somehow.
Very occasionally, with the 3db shelf, I notice some deeper female voice can give a sense of 'authority' that I have never heard before.
When it happens, it notably raises my heart rate a little. I have had this effect with very large speakers (JBL 15inch bass units with 18inch subs) in smaller rooms, but have never noticed it on female voice, and certainly never with IEMs.
Even if you don't keep it at the level, I highly recommend turning the bass up for a trial with these IEMs. It shines on unusual tracks with overblown bass concurrent with other instruments that other IEMs can't separate the details.
With speakers, I find you need really massive bass drivers to keep the life in a track, or is sounds like a poor recording (JayZ comes to mind) these IEMs excel with complex tracks like metal also. Try 'no church in the wild' and notice all the complex background reverb/breathing and details that are normally lost with the deliberately distorted bass (the cracking in the track at about 2.10 is in the recording by the way).
Alternatively Jay Z 'holy grail' becomes a really good song, rather than 'average' somehow.
Or good old Led Zeppelin where it holds all the instruments separately when you turn it up as the dynamic range is quite high.