Whichever one you already have right now.
Cause how would you vote on which voting system to use for voting on your voting system?

The second best one.

Each voting system should select a champion. The champions then fight to the first blood. Last champion standing wins.

Maybe something with chads.

Chicken run.

You try every voting system and then measure which one is best through determining which one got the best results.

The best voting system will be decided by statistics, not democracy to see which most accurately represeted the individual interests of the masses.