As a true one-handed minimalist phone user, the 5.4” gets closer but doesn’t cut it for me. The 5/SE1 is the biggest phone and screen size I want, because, as Apple advertised, the iPhone 5 was the biggest phone and screen possible for true one-handed use. Even a mm bigger in either body or screen size, and there is a big drop off in the ease of one-handed use. So the phrase “so close, yet so far” can be very true in regards to this.
I use a phone primarily outside where I only need to accomplish quick tasks and maybe listen to audio, but not watch a movie, look at photos, or read for extended periods (by principle that’s the kind of thing I only do at home, which is also where I can switch to a bigger more ideal device). So a bigger screen phone really does not benefit me, but only inconveniences me. But I realize my phone usage is different than most.
I’m glad some find this the ideal size for them. And while it may be better for me than what was there before, it’s still “so close, yet so far”.
edit- actually the SE2 will probably be a little better for me, since it’s about the same size but the screen is smaller therefore easier to reach with my thumb.