For sure, I've been thinking a lot about this myself for the past day that I've had the LX. The two put forth very different sound signatures-- and personally I find them very complementary. With the LX the whole signature is defined by the bass-- it's large, it's powerful and it's everywhere. Thankfully it's also very resolving and detailed so that the rest of the sound isn't drowned out in the bass. Nonetheless the bass is present and it dominates. Consequently the mids, particularly vocals, while sufficiently bodied and robust, are pushed back a bit behind the bass...but this is true in any V-shaped monitor. The result, I find, is that the sound is a bit "closed in"...I wouldn't go so far as to say congested, as one of the great things about LX is that it somehow avoids this despite all the bass...it's why I would call it the ultimate "basshead audiophile" IEM. Nonetheless, due to the robust low end on the LX it can be said to be lacking a bit of air.
The Solaris, on the other hand, is an entirely different beast. Whereas the LX does the "v-shaped club sound " better than anything else I've ever heard, the Solaris gives you a sense of air and space and a holographic stage-- I have not encountered any IEM, and I've tried many, that can replicated the sense of 3-d space and separation of sounds that Solaris creates...it's simply breathtaking. Consequently everything has more space to breath, vocals are more forward, and there is more thickness in the mids overall. The bass is still present and impactful. but it's at the centre of a vast space rather than dominating the mix. With the LX I feel as thouh I'm at the club, on the floor with the bass pulsating around me, with the Solaris I feel as though I'm inhabiting a vast space with detail and sound coming at me from all directions.
What's interesting to me is that with each IEM I can listen to the same track and enjoy it in two different ways. Take for instance Ice Cubes "Amerikkka's Most Wanted" off the album of he same name. It's one of my favorite hip hop tracks and it's driven by a deliciously textured and deep bassline. On the LX this bass is brought to the forefront and it really gets you going, with the lyrics retreating to the background a wee bit. On the Solaris, the same texture and rumble is there in the bass, but it's in the background while Cube's voice is more in the foreground and it feels as though he's rapping right into your ear. The sound on the whole is a tad cleaner & clearer and much more spacious. I enjoy the presentation of each equally, depending on my mood. I love both and would still consider Solaris my favorite IEM as it ticks all my boxes and is a better "all rounder to me"...but the LX is a fantastic "partner in crime" for the times when I want a more robust, pounding club type sound-- it is peerless in that regard. Hope this helps.