I don't think you can compare the sem1 to sem5 as one is open and one closed .but to me, key words to me, the sem5 we're a better , more organic, wider soundstage, more holographic than the elegia .
No knock on the elegia as I don't think they are hyped but unless you have a reference, everything you listen too is the best at that point in time . I thought the elegia we're my precious, but along came the sem5 and the elegia lost it's lustre to me. Now maybe the open back sem1 sound different than the sem5, better? Maybe, maybe not. All a point of reference.
Right now I'm pissed I bought the UE 18+pro as they share a very similar sound presentation to elegia. Alas I want an CIEM that is similar to the sem5 .so now I don't listen to the UE as I crave the sound of the sem5
All my opinion