I tried to install OSMC but didn't succeed so I installed Kodi on top of Raspbian and set it to autostart.
Will there be any performance difference I may notice ?
It's never had that and NOOBS appears to have been functionally stabilised (last update was a cosmetic change for RPi3B+). PINN has an option to refresh an installed OS without trashing everything else on the SDCard.
NOOBS full brings some OS ( RASPBIAN desktop ...) can change with the version...