I found the 4P too bass shy and / or too shrill in the treble. There's a big treble peak I was EQing out before they broke
(that's the inverse of my EQ settings, ie their deviations in frequency response from my ideal; red is SHE3580, black is ER-4P)
I doubt such a minor tweak as the 4P-4S conversion (which I hear emphasizes the treble even more anyway) would have helped.
As you can see, objectively the 4P looks closer to my ideal than the SHE3580, but not close enough to sound much good without EQ and that meant they were equally useless in non-EQable applications. Since then I've strived to expand the scope of EQable applications and now with VAC+VSTHost everything on the computer (including YouTube and stuff like Spotify) can pass through Electri-Q. I'm still looking for something that will sound good on my phone when using anything other than PowerAMP though... (again, stuff like music streaming services)