screen size and quality vs speaker sound seems like a very odd trade off. i listen to a good amount of music on my phone. however, 99% of the time it's with headphones. at the gym, in the yard, at my desk at work...there's very few places i can play music without headphones (without being inconsiderate) and actually enjoy it. i can respect that the one has great speakers, but how often can you use them? the speaker function for me is pretty much only used as a hands free convenience or while on a call.
screen size vs physical size of the device speaks for itself. everything revolves around the screen.
Emphasis added because your mileage may vary.
I use my phone speaker very often and am dissatisfied nearly half the time.
If I get the One then I'll be set on that, and will pick up the JBL Flip when it suits my fancy (I'm sold on that).
If I get the SGS4 then I'll be getting the JBL Flip on the same day, no option for me on that.
Phone calls are not all about the screen, neither is enjoying music at my desk courtesy of my phone.
The trade-off that you won't use or see creates the requirement for an immediate accessory purchase for me.
No kidding - choosing the larger screen for me means often I'll have to carry and charge two devices rather than just one. And I may just do that. But just the SGS4 alone or continued use of an inadequate speaker phone on many occasions? Not my choice for my next upgrade, or it won't be an upgrade.
I use headphones as well - but at my desk or in my lab, they're inconvenient and the speaker use is inconsiderate to no one.
As I like to say, your mileage may vary.