IMO the ZX10R is the best sounding flatplane I4 superbike
The S1K lacks character. It sounds like any of the 600s but without the charm of the extra revs. The fireblade sounds better and more unique but not as intimidating as you’d want.
The ZX10R on the other hand has this angry and raw sound. Only way I can describe it is it still screams but there is much more bass and resonance to it. I have an arrow exhaust on mine and it sounds like Godzilla approaching to destroy your city.