Absolute Will would win, and here's why:
See, Supreme Voice requires one to speak in order to do anything, while Absolute Command similarly requires you to issue a command. In other words, both are active powers that require one to actively use them.
Absolute Will on the other hand is not only actively used, but also passivley used. Additionally, it's active use is thought-based. So, in the time it would take for one to speak (SV) or issue a command (AC), Absolute Will would have won.