Dave Hall used to say that some of his preamps would run at 9V but would give much better performance with 12 or 18. Sadly he's no longer around to ask.
I have an elderly Ibanez chorus pedal from the 80's which requires 18V, but the first circuit drops the voltage down to 12V. Maybe this was Ibanez's way of coping with sagging analog batteries.
I also have a Triton overdrive which includes an internal 'pump' circuit to increase the 9V supply to 18V. I guess that Triton know what they are doing and aren't doing this just to be clever, so there must be some practical benefit. Empirically, it's an excellent sounding pedal so I'm a believer.