Ohhh, this is one of my favourite topics. As professional I use to deliver my works at 48KHz and 24bit. I think it’s a good professional quality, and I’m sure the customer can listen to it.
I can hear the difference between 44.1KHz and 48KHz in a good hifi system (more brilliance and defined sound). 96KHz and 192KHz are more academical stuff. I mean that it’s difficult to hear the difference with common music. BUT if you use specific synthesizers, as example, the difference is HUGE! more harmonics, more high frequencies. Definition is superb! Indeed 192KHz would be my choice but customers could not appreciate or have a machine capable to read it. So better to go back to well known 48KHz.