The LCD-X have my favorite sound signature of the cans I own. They're pretty uncomfortable though, which is a combination of their heavy weight, large size, and poorly designed suspension whose smallest setting is slightly too big for average sized heads. Because I enjoy the sound signature so much, I use them for dedicated listening sessions. For regular use headphones that you throw on and off because you're stepping away from your computer or whatever, the LCD-Xs are inconvenient.
I have the Aeon closed 1. They are more comfortable and convenient than the LCD-X. They have a good sound signature but generally weaker than the LCD-Xs. The LCD-Xs have better bass extension, punchier base, a wider soundstage, and the LCD-Xs also sound "faster" than the Aeons, as in songs anecdotally sound crunchier and hits sound punchier. I think this adds to slightly better sound of instrument separation in the LCD-X as well. The Aeon 1s closed still sound very good though, just a small class below the LCD-X. The Aeons also fit really well due to their ear shaped cup design, at least at first.
The Aeon 1 has two infuriating design flaws: the gimbal suspension gets weaker over time so the headphone height adjustment gets easier to slide around, making it less stable on your head. And the worst feature is that the foam in the pads can twist, meaning your ear pads will no longer hold the right shape over time. Dan has a
very poorly done video on a strategy to correct the twisting, which doesn't work.
Frankly, the design flaws of both the LCD-X and Aeons are inexcusable for their price. They're both overpriced and need a makeover.
TL;DR for sound LCD-X every time, for general purpose headphones you want to use a lot, Aeon closed. I plan to keep both in my collection for the foreseeable future.
FWIW, I use my Aeon closed as my main work headphone, when I'm passively listening to music and working. Currently these are what's on my head most of the time. The Aeons sound great, and I don't care if I'm missing out on the really 𝕤𝕝𝕦𝕥𝕓𝕒𝕘 bass and juice from the LCD-Xs when I'm working. I use my LCD-Xs for when I want to get ᖇEᗩᒪᒪY ᔕᒪᑌTTY and have some sick dedicated listening sessions. Like if my favorite artist or friend releases a new track, I demo it on the LCD-Xs first to get the full effect.
When I get tired of the weight of the LCD-X, I switch to the Focal Clears, which are lighter, but don't have as juicy of a bass extension as the LCD-Xs.
