Political world building, next on Nov. . .no. Wait. I'm not PBS. Sorry. Still. We are examining the merits and deficits of governmental bodies in our world building.
The original question was president or monarch - I'd like to think that from a SF standpoint there are more options than that, but you wouldn't know it based on my work. My answer to the question is: Both. At the very least. Because in my main SFR series, I have at least four separate populations vying for territory and resources, I have more than one option for structuring governments.
Confession time. Never, ever in my life did I aspire to write political stories. At. All. Yet here I am, having painted myself into a corner because you can't write military-ish SFR without talking about the governments that send people into battle in the first place and the philosophies for which they're fighting. Whether for good or for ill.
Tagreth Federated Council - this is a presidential government and several chamber council system that knits a group of planets together into a pooled resource. It has draw backs because the seat of government shifts world every few years so that no one world gets all the economic advantage or becomes the seat of power. Until a ruthless, power-hungry man who thinks he's the only one with all the right answers gets hold of the reins. Things go bad fast. My heroes and heroines have to claw their way back up from the debris pile before they can do anything like damage control.
The Claugh nib Dovyyth Empire - this is a monarchy. The queen has her nobles council and her elected council of the people to which she's beholden, but she has very broad latitude, especially when it comes to serving the people. So you don't often see her cowering in a corner while the bad guys are attacking. She's usually out there on the front lines. She's more than a figurehead, less than a living god. If that makes any sense. She's young and open-minded about how a royal ought to go about ending a war. So she's willing to make alliances no one else would consider. It's earned her a few enemies. Some of them roost close to home.
The other three governments that I can think of in the books all operate based on councils. There may be a single leader at the front of that council. Or a trio. Or some number. But the point is that in SFR having just one person standing up in front saying, "This is how it's gonna be just because I say so." is only going to last as long as someone showing up with a laser pistol and really good aim. But give a population the feeling that they're represented and at least partially heard? They'll wait for someone else to rise against the government.
The only thing I wonder is whether the people in my made up worlds avoid answering the phone during election cycles the same way that I do.