It's a hard question to answer. It all depends on the music and personal preferences really.
I would say the Semper, for me at least, works best with blues, classic rock and rap. The vocals and electric guitars sound incredible on them. The bass is amazing too. Similar to OM , but a bit more quantity.
The MEST, mine is the OG, does EDM and modern music very well. Imaging and soundstage is its strong points. Bass is of high quality too and has good amount of subbass.
The Solaris is more balanced, more mid centric, nice punchy bass but lower quantity to the MEST. It sounds more analogue and natural compared to the MEST. It's quite holographic and the stage is very wide and enveloping overall. Works well with a lot of genres.
With the Elysium I haven't spent much time yet. But so far I can say the midrange is sublime . Natural instrumental timbre, cohesive and refined sound, engaging vocals. Stage a bit narrower and it's a single BA bass with quantity to others bit with good texture and clarity. It works with a lot genres IMO. More so with classical, singer songwriter, metal and jazz I think.
That's all I can think of now, hope that helps.