I prefer my music to sound close to me as opposed to making it feels like a concert that you get on headphone or speakers, so I chose IEM any day. When comparing items at the same price, I very much prefer Andromeda compared to DCA Aeon 2 or Audeze LCD-2, they just sounded more pleasing and more practical to me. Of course, the soundstage is much bigger in headphones but I can feel note textures and details better in IEM.

Edit: I already got to the point where the only headphone I keep is LCD-2 for 7 sake, but I rarely use them, maybe only a few days a month. I suggest OP try both himself and find what you like better.