Hi,
Please confirm: you are talking about gate drive voltage
I think this is development the wrong way round. In my eyes it makes no sense to start with gate drive voltage.
Start with your "real" requirements, like input voltage, output voltage load current, efficiency, switching frequency...
Indeed I see no benefit in driving a MOSFET gate higher than 12V or 15V.
For more detailed and more reliable informations I recommend to read datasheets of Mosfets and application notes about Mosfet gate drive design.
Modern MOSFETs are fully ON with V_GS of 7V. And the change in R_ds_on above this voltage is only marginal.
Thus driving with higher voltage than 12V makes not much sense.
On the other hand many MOSFETs specify the "absolute maximum voltage" with +/-20V. Any tiny overshot in time and voltage may harm the MOSFET. I don't know a single MOSFET where V_gs of 20V is specified as "recommended operation condition".
Don't risk early dying of the MOSFETs.
Increasing V_gs mainly increases the charge that is pushed into the gate....and exactly this charge needs to be dissipated when the MOSFET has to be switched OFF. This not only means increased gate drive power that will generate heat, it also means increased switching delay.
Klaus