Monarchy
The people are going to voice out and participate regardless. It's not like there's never a way to influence power. Monarchy is better for actually vetting pieces against a set criteria since there's only one consistent view judging every piece. It's useful for some focused pieces, but not for people.
Honestly, democracy is my go-to for making challenges because I promise I will forget to choose a winner most of the time. While that makes it harder for smaller accounts and new accounts to 'win' and gain traction, it's more convenient.
Realistically though, between the two extremes, democracy is susceptible to the dangers of stupid people in large groups much more than the dangers of tyranny. Not that either are good ways to organize, but a central power is more manageable than having the power sit with an everchanging majority.
Plus, it's easier to assassinate one bad monarch than an entire cult.
I mean, In monarchy challenges, participation is voluntary. In the real world, ah....