Tricky question this. I’ve got some fantastic headphones (in my flair) of which probably the most used are my HD-650 lately because of comfort, but if I had to choose just one it might be the Blessing 2 Dusk. Those things are honestly insane. I never thought IEMs could possibly come close to over ear and I only bought these for listening in bed without disturbing my wife, but wow. They blow me away every time. Of course there are things my over ears can do better (like soundstage), but the portability and bed friendliness of the IEMs gives them a level of utility that I couldn’t do without for my sole listening device. Plus they sound good enough that I would never really miss the others.