It's interesting, I was discussing this exact thing in relation to Z1R and EXT with
@xenithon. To paraphrase, xen used the same word to describe the EXT as you do:
immersive. In his opinion (and feel free to chime in here
@xenithon), Z1R
presents the music to you, whereas with EXT you're part of the music. With Z1R you're at the concert watching it with the crowd, with EXT you're on the stage.
None of this is to say one is better than the other. It really depends on how you prefer to experience your music. You might enjoy both experiences equally, and if so, own one or more IEMs to give you varying levels of each.
What came out of our chat is that I seem to generally prefer the way Z1R presents the music to me, allowing me to take in the whole, whereas with EXT I'm immersing myself in different parts of the music and not always taking in the whole performance.
An analogy I used is 3D vs 2D films. As impressive and 'immersive' as some 3D films can be, they demand the viewer gets involved with the visuals, walk around the scene and its elements. In contrast, a 2D film is presented to you with a certain structure, a vision from the director and cinematographer as it were. With a 3D film I often get taken in by certain elements and forget to take in the 'whole', whereas with 2D films it's more about the story and how all the elements work together.
To sum up, I personally prefer sitting back and having the music presented to me, interpreting the story of the music in my mind's eye. I also enjoy the experience of immersing myself in the various soundscapes and elements, but less so than the former.
Questions back at y'all: which do you prefer? Is it more 'real' to you to be in the audience or be on stage? Do you prefer immersion, or to sit a few rows back and take in the performance as a whole? And which IEMs give you one or the other in different ways?